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The effects of redd site selection and redd geometry on
the survival of incubating Okanagan sockeye eggs.
by
Karilyn Ingrid Long
Bachelor of Science, University of Victoria, BC 1998
A Thesis, Dissertation or Report Submitted in Partial Fulfillment of the Requirements for the Degree of
Masters of Science
in the Graduate Academic Unit of Biology
Supervisors: Richard Cunjak, PhD, Canadian Rivers Institute, UNB Robert Newbury, PhD, Canadian Rivers Institute, UNB Examining Board: David Scruton, PhD, Federal Fisheries and Oceans
Kerry MacQuarrie, PhD, Civil Engineering Depart., UNB
This thesis is accepted by the Dean of Graduate Studies
THE UNIVERSITY OF NEW BRUNSWICK
October 2006
© Karilyn Long, 2007
i
ABSTRACT
This study explores the spawning process of Okanagan sockeye salmon
(Oncorhynchus nerka). Natural and channelized reaches supporting spawning sockeye
were studied for suitability as spawning grounds. The scope of this work is two-fold.
Firstly, hydraulic characteristics found at redd sites in spawning grounds were
measured for depth, velocity, and two flow parameters, the Froude and Reynolds
numbers. Only Froude numbers (Fr = 0.315 ± 0.10) were found to be similar between
the two reaches implicating this characteristic as selected for by spawning sockeye.
The natural reach contained this range of Froude numbers in both years sampled,
where the channelized reach contained this range during lower than average discharge.
Secondly, flow through the redd was studied for its impact on egg survival using the
redd steepness and the composition of the bed materials as factors that affect the terms
in Darcy’s Law of groundwater flow. Redds with either higher fine sediment
accumulations or less steep redds were found to support lower rates of egg survival. In
the channelized reach where fine sediment accumulations were higher, salmon may
need to build larger redds, which may be costly to the fish in terms of energy reserved
for the task in these the final stages of their life cycle.
Moving away from a homogeneous environment will increase likelihood of preferred
spawning and incubation flows therefore improving egg (and species) survival.
ii
ACKNOWLEDGEMENTS
I would like to thank the University of New Brunswick, Canadian Rivers Institute and my
committee Dr. Rick Cunjak, Dr. Bob Newbury, Dr. Katy Haralampedes, Dr. Kim Hyatt,
and Dr. Allan Curry who have been generous with their time and support.
Also thanks for the generous support of the Okanagan Nation Alliance Fisheries
Department for letting me borrow so much of their equipment and many of their
technicians as well as the time off to pursue this endeavor (Pauline Terbasket and
Deana Machin). The Katim students that helped collect river measurements in many of
those cold winter sessions were well appreciated (Lynnea Wiens and Natasha Audy).
I am completely indebted to Rachel Skrlo who put in many hours editing and tirelessly
explaining to me the fundamentals of good grammar. Thanks also to Dr. Douglas
Peterson (CRI) and Dr. Robert Houtman of the Pacific Biological Station and Chris Bull
for their time in editing and providing valuable comments.
Funding for a portion of the report was provided by Douglas County Public Utility District
through the Fish-Water Tools Committee. Thanks to the Shuswap and Summerland
Hatcheries for the help collecting and verifying fertilization of sockeye eggs.
My dad was a great help building some of the equipment needed, tirelessly modifying
gear to suit my particular taste. Finally, this would not have been possible without the
support from Herb and Chloe, who moved across Canada and put up with me making a
racket at all hours of the night trying to get this done.
Thanks
iii
TABLE OF CONTENTS
ABSTRACT ........................................................................................................................ i
ACKNOWLEDGEMENTS.................................................................................................. ii
TABLE OF CONTENTS ................................................................................................... iii
LIST OF FIGURES............................................................................................................v
LIST OF TABLES ............................................................................................................. vi
1.0 INTRODUCTION.........................................................................................................1
2.0 SELECTION OF SPAWNING SITES BY OKANAGAN SOCKEYE SALMON ............9
2.1 INTRODUCTION.........................................................................................................9
2.1.1 Study area and timeline.................................................................................12
2.1.2 Hypothesis and predictions ...........................................................................14
2.2 METHODS ................................................................................................................16
2.2.1 Redd site measurements...............................................................................16
2.2.2 Measurement of available spawning area .....................................................18
2.2.3 Statistical analysis .........................................................................................19
2.3 RESULTS..................................................................................................................20
2.3.1 Redd site measurements...............................................................................20
2.3.2 Grid surveys ..................................................................................................22
2.3.3 Measurement of available spawning area in grid sites..................................25
2.4 DISCUSSION ............................................................................................................27
2.5 REFERENCES..........................................................................................................33
iv
3.0 OKANAGAN SOCKEYE EGG SURVIVAL................................................................40
3.1 INTRODUCTION.......................................................................................................40
3.1.1 Study area and timeline.................................................................................46
3.1.2 Hypothesis and predictions ...........................................................................49
3.2 METHODS ................................................................................................................50
3.2.1 Egg survival ...................................................................................................50
3.2.2 Inter-gravel Dissolved Oxygen ......................................................................57
3.2.3 Hydraulic conductivity measurements ...........................................................58
3.2.3 Hydraulic gradient estimates .........................................................................60
3.3 RESULTS..................................................................................................................63
3.3.1. Egg survival ..................................................................................................63
3.3.2 Inter-gravel Dissolved Oxygen ......................................................................65
3.3.3. Hydraulic conductivity measurements ..........................................................67
3.3.4. Hydraulic gradient estimates ........................................................................69
3.4 DISCUSSION ............................................................................................................69
3.5 REFERENCES..........................................................................................................76
4.0 CONCLUSION ..........................................................................................................85
APPENDIX 2-A: Summary of salmon spawning site selection research.........................87
APPENDIX 2-B: Measurement taken above redd sites selected ....................................90
APPENDIX 2-C: Physical features of the river available to spawning sockeye...............92
APPENDIX 3-A: Fertilization success estimates .............................................................94
APPENDIX 3-B: Pre-hatch incubation survival of sockeye eggs in 2002........................95
APPENDIX 3-C: Invertebrates found within incubation baskets upon recovery 2003.....96
v
APPENDIX 3-D: Pre-hatch incubation survival of sockeye eggs in 2003........................97
APPENDIX 3-E: Intra-gravel dissolved oxygen measurements ......................................98
APPENDIX 3-F: Fine sediment accumulation within incubation baskets ........................99
APPENDIX 3-G: Summary of sockeye built and artificial redd measurements .............100
Curriculum Vitae
LIST OF FIGURES
Figure 1.1 The Okanagan River, a tributary of the Columbia River.............................. 2
Figure 1.2. Photos of the study area ............................................................................ 3
Figure 1.3 Salmon redd being built (Burner 1967) ....................................................... 4
Figure 2.1. Okanagan River study area........................................................................ 8
Figure 2.2. Example of site photo with a grid overlaid................................................ 11
Figure 2.3. Okanagan River average monthly flows (Water Survey of Canada)........ 12
Figure 2.4. Distribution of the variables measured at the Site 4 grid (natural reach). 14
Figure 2.5. Location of redds and distribution of Froude numbers in the four grids ... 14
Figure 2.6. Ranges of Froude numbers available in the two reaches over the two years
studied. ........................................................................................................ 15
Figure 2.7. Depths and velocities documented at Okanagan sockeye spawning sites
with Froude numbers 0.2, 0.3 and 0.4 overlaid ........................................... 16
Figure 2.8. Ranges and means of Froude numbers documented for spawning Atlantic
and sockeye salmon. ................................................................................... 17
Figure 3.1. Salmon redd profile (White 1942)............................................................. 26
vi
Figure 3.2. Multi-scale processes potentially controlling intergravel flow near redds
(Zimmerman and Lapointe 2005) ................................................................ 27
Figure 3.3. Flow paths through gravel with a surface similar to a redd ...................... 28
Figure 3.4. Flow paths with a level gravel surface (Cooper 1965) ............................. 28
Figure 3.5. Okanagan River profile with the reaches and sites identified................... 29
Figure 3.6. Incubation baskets as it is placed within the substrate............................. 31
Figure 3.7. DO extracting vet probe and Oxyguard meter.......................................... 36
Figure 3.8. Redd profile showing the relation between the hydraulic gradient and the
redd steepness. ........................................................................................... 38
Figure 3.9. Redd profile labelling dimension measurements...................................... 38
Figure 3.10. Average pre-hatch egg incubation survivals by habitat types in 2003 ... 40
Figure 3.11. Intra-gravel Dissolved oxygen measurements ....................................... 41
Figure 3.12. Ranges of accumulated fine sediment by reach in 2003........................ 41
Figure 3.13. Ratio of sand to fine sediment size fractions (by weight in grams) ........ 42
Figure 3.14. Profiles of redds artificial and built by sockeye in the two reaches ........ 44
LIST OF TABLES
Table 2.1. Mean and standard deviations of variables measured in the two reaches
measured in 2002, 2003 and 2004 ................................................................13
Table 2.2. Overview of redd site characteristics of sockeye............................................13
Table 2.3. Available Froude numbers in the reaches in the two years sampled .............15
Table 3.1. Mean and range of egg survivals in the three reaches in 2003......................40
Table 3.2. The mean gradient of artificial redds and redds built by sockeye...................42
1
1.0 INTRODUCTION
This introduction is intended to tie together the following multi-chapter thesis and
present common background material. Section 2.0 compares the types of flows, or flow
hydraulics, in the natural and channelized reaches of the Okanagan River to measure
frequency of flow type preferred by sockeye salmon (Oncorhynchus nerka). Section 3.0
studies the survival of sockeye salmon eggs in the same reaches as well as the
variables that control water flow to the eggs, an essential element for ensuring survival.
Flow hydraulics has been selected as the variable of interest because little research
has been done to assess the impact this characteristic has on redd site selection. The
two flow hydraulics assessed are the Froude number (Fr), which measures the
relationship between gravitational and inertial forces, and the Reynolds number (Re),
which measures the relationship between inertial and viscous forces. Using both
qualitative and quantitative analysis, this research will add to the community’s general
understanding of salmon spawning environment preferences.
Background research includes a literature review and an environmental assessment of
selected characteristics – such as velocity, depth of water, and flow hydraulics –
present throughout the natural and channelized reaches at redds, or nests, built by
salmon where their eggs incubate. Once the environmental characteristics are
measured, a quantitative analysis is done to determine which characteristics are
dominant at the redd sites. Finally, the summary recommends, based on these findings,
best practices for effective streambed restoration projects.
2
This paper examines an initiative led by the Canadian Okanagan Basin Technical
Working group (COBTWG) to restore one kilometre of the channelized reach where
sockeye spawn. The question asked is ‘Does restoring a channelized reach to replicate
flows found in a natural reach increase the amount of spawning areas and improve
incubation flows?’ The restoration of the uniform channelized reach would create
habitats similar to the natural reach with meander bends, islands and bars, pools and
riffles, a functional floodplain and riparian vegetation. Of the factors affecting spawning
and egg incubation, this research has focused on the types of river flows (or flow
hydraulics) selected at spawning sites and the flows through the substrate of redds
required for successful incubation of sockeye eggs.
Sockeye salmon spawn in the Okanagan River, which is a tributary of the Columbia
River (Fig.1.1). Of the 30 sockeye stocks that once inhabited the Columbia basin,
Okanagan sockeye are the last of two runs and make up 50% of all Columbia sockeye
production (Fryer 1995). Not only has the number of stocks declined, but abundance of
this stock has fluctuated dramatically with an overall decline in the last fifty years (Hyatt
and Rankin 1999). The decline can be partially attributed to habitat degradation and
channel modification (Summit 2003) since much of the river was dyked and channelized
in the mid 1950’s for protection against floods.
3
Courtesy of the Salmon in Regional Ecosystems Program
Figure 1.1. The Okanagan River, a tributary of the Columbia River
4
Only seven percent, or six kilometres, of the river remains in an unaltered state –
termed the natural reach for the purposes of this thesis – with features such as
meander bends, islands and bars, a functional floodplain and riparian vegetation (Fig.
1.2a). The remaining 17 km is a straight channel with a trapezoidal-shaped cross-
section that is dyked right to its wetted width and devoid of riparian vegetation. This
section also contains 13 Vertical Drop Structures (VDS), cement walls that span the
river (Fig. 1.2b). The VDS, put in place when the river was channelized to reduce the
steepened slopes of a straightened river, has a uniform, trapezoidal-shaped cross-
section that moves water at homogenous velocities. This contrasts the cross-section of
the natural reach which has bars and islands creating a variety of depths and velocities.
Fluctuations in stream discharge (the amount of water moving through the cross-
section, measured in cubic meters per second) causes different effects in the two
reaches; however, the channelized reach’s will remain homogenous and the natural
reach’s will be heterogeneous.
The first VDS (VDS13) is located two kilometres downstream of the natural reach. The
reduced gradient in the back flooded channel above the weir causes deposition of
spawning sized gravels as they migrate downstream from the natural reach. Since its
creation, this short section of the river – termed the channelized reach – has
accumulated gravels that are used by spawning sockeye (Fig. 1.2c). Downstream of
VDS13, the remaining 18 km of the river contain deep slow moving flows and infrequent
patches of spawning gravel that are punctuated by VDS12 through VDS1 before
emptying into Osoyoos Lake. Because of the slow flows and lack of spawning gravel
this large reach that was productive before channelization is no longer suitable for
spawning.
5
a. The natural reach
b. Typical Vertical Drop Structure
c. The channelized reach
Figure 1.2. Photos of the study area Courtesy of the Okanagan Nation Alliance
6
Okanagan sockeye spawn in both the short channelized reach above VDS13 and the
natural reach upstream. They build redds, or nests, in the gravel substrate. Fertilized
eggs are deposited into the redds to incubate, which is a sensitive portion of a salmon’s
life history. Typically, at this stage only 7% of the eggs survive to hatch and emerge
from the gravel redds (Bradford 1995). Eggs are deposited in the fall, over-winter, and
then emerge in the spring. The emerging fry migrate downstream to Osoyoos Lake
where they rear for one year before further migrating 1200 km through the Columbia
River to the ocean where they spend two years. The fish complete their life-cycle by
returning to the Okanagan River to spawn.
The flow types that salmon select at spawning sites were selected for investigation
because salmon are known to spawn at transitional areas between pools and riffles,
otherwise known as riffle crests or pool tails. The characteristics at these transitional
areas can be quantified with equations such as Froude and Reynolds numbers, which
describe flow in terms of turbulence or states: deep and slow, or shallow and fast
moving (rapid flow). Chapter 2.0 compares Froude and Reynolds numbers with water
depth and velocity measures that are traditionally recorded (Burner 1951; Knapp and
Vredenburg 1996; Lacroix 1980; Montmery et al. 1999; Muller and Hubert 1995;
Parsons and Hubert 1988; Shirvell and Dungey 1983; Smith 1973; Thurlow and King
1994) at sites selected by spawning sockeye to determine if the Froude or Reynolds
numbers are better predictors for preferred spawning sites. Available Froude and
Reynolds numbers were assessed in natural and channelized reaches to determine if
they were preferred by spawning sockeye salmon over the two years studied (2002 and
2003).
7
Once spawning sites are selected, sockeye, like all salmon, build redds in the gravel
substrate to lay their eggs. Redds function to protect the eggs buried within them while
allowing flow through the redd substrate. The flow carries needed oxygen and removes
waste products (Chapman 1988; Lisle 1989). In Chapter 3.0, the survival of sockeye
eggs is measured in artificial redds in the two study reaches and related to a number of
factors known to affect survival. The two most commonly documented factors are inter-
gravel dissolved oxygen, IDO, (Wood 1995; Pauley et al 1989; Bams 1969; Emmette et
al. 1992; Brannon 1965; Peterson and Quinn 1996) and fine sediment accumulation
(Bams 1969; Koski 1966; Dill and Northcote 1970; Bjornn and Reiser 1991; Argent and
Flebbe 1999).
Although fine sediment accumulation was assessed when looking at the egg incubation
environment, recent work by Zimmerman and Lapointe (2005) found that significant
inter-gravel flows can be triggered through the length of the redd in response to redd-
scale water surface gradient and the relatively higher conductivity of the redd patch,
after spawner activity. Fine sediment accumulation is known to reduce the hydraulic
conductivity of the substrate. Hydraulic conductivity along with the hydraulic gradient of
the stream bed are the two factors that produce inter-gravel flow, according to Darcy’s
Law of groundwater movement (Knighton 1998). It is the water flow that brings IDO to
the eggs ensuring their survival (Quinn and Foote 1994). Chapter 3.0 also looks at the
added effect of a redd steepness – represented by the shape of redds built by sockeye
(Fig. 1.3) – as the morphology of the bed is known to affect the hydraulic gradient that
in turn affect the amount of flow through the gravel substrate that makes up the redd,
which affects egg survival in the natural and channelized reaches.
8
Figure 1.3. Salmon redd being built (Burner 1967)
The concluding chapter (4.0) summarizes key findings to determine the effects of a
restored channel on spawning sockeye and their incubating eggs if flow hydraulics are
considered when completing the restoration. Additionally, this chapter will discuss a
general application of these findings to other species, other rivers and other studies.
Hummock
Trough
9
2.0 SELECTION OF SPAWNING SITES BY OKANAGAN SOCKEYE SALMON
2.1 INTRODUCTION
The topic of spawning sites may inspire over-generalization due to species, race1 and
individual variations (Kondolf 1988). In addition to these variations selecting which
physical factors to analyze is difficult because environmental variables in streams are
typically correlated and confounded with one another (Reid 1961 in Platts 1976; Heede
and Rinne 1990). Adding to this perplexity is stream dynamics, which changes daily and
especially yearly (Platts 1979). Therefore, it is not surprising that although significant
research on salmon spawning behaviour has been done, it remains unclear which
variables salmon select in spawning sites (Montgomery et al. 1999; Foerster 1968). It is
known, however, that salmon utilize only a fraction of the apparent available streambed
for spawning. For example, Atlantic salmon (Salmo salar) was found to use only 2.8%
of the apparent available spawning areas of a New Brunswick stream (Lacroix 1980).
While the primary focus of this paper is to examine the impact of flow hydraulics – or
types of flow – on spawning site selection, they are recognized as only one of many
possible characteristics affecting this selection (Barnard 1992; Briggs 1953; Hazzard
1932; Hobbs 1937; Hunter 1991; Moir et al. 1999; Smith 1941; Stuart 1953; Stuart
1954; White 1942; Appendix 2A). Other variables include: water depth and flow velocity
(Burner 1951; Knapp and Vredenburg 1996; Lacroix 1980; Montgomery et al. 1999;
Muller and Hubert 1995; Parsons and Hubert 1988; Shirvell and Dungey 1983; Smith
1973; Thurlow and King 1994), stream discharge (Benda et al. 1992; Chapman et al.
1986; Cowan 1991; Montgomery et al. 1999; Thurlow and King 1994), stream gradient 1 Fish have different races – more commonly called stocks – such as the Okanagan sockeye, Stuart River
sockeye, and Red Lake sockeye. They are the same species and could interbreed, but each are so different that if they were transplanted they likely would not survive because of developed differences. For example, one race spawns in lakes, others only in rivers etc.
10
(Benda et al. 1992; Crisp 1996; Mills 1973), substrate sizes (Baldrige and Amos 1981;
Burner 1951; Hasler and Scholz 1983; Hoopes 1972; Lacroix 1980; Muller and Hubert
1995; Needham 1961; Platts et al. 1979 in Barnard 1992; Reiser and Bjornn 1979;
Tautz and Groot 1975), bed stability (Hartman and Galbraith 1970; in Lacroix 1980),
biological factors, such as competition and predation (Blair and Quinn 1991; Gibson
1993; Shirvel and Dungey 1983), groundwater and substrate permeability (Burner 1951;
Crisp and Carling 1989; Curry and Noakes 1999; Geist and Dauble 1998; Lacroix 1980;
Stuart 1954; Tautz and Groot 1975 in Thurlow and King 1994; Webster and Eiriksdottir
1976; Witzel and MacCrimmon 1983), and inter-gravel dissolved oxygen (Wood 1995).
The ability to describe flows has been articulated in engineering texts for centuries as
predicting flow hydraulics is essential when constructing canals or restructuring
riverbeds (Chow 1959). Flowing water is governed by the forces of gravity, friction,
viscosity and inertia (Giller and Malmqvist 1998). The force of gravity moves the water
downhill while the force of inertia reflects the water's ability – or lack of it – to move.
Two unique measures of flow hydraulics are the dimensionless Reynolds and Froude
numbers. The relationship between the inertial forces and the viscous forces
determines the degree of turbulence in the flow and is described by the Reynolds
Number, Re (Heede and Rinne 1990). The relationship between gravitational and
inertial forces is described by the Froude number, Fr.
The Reynolds number (Re), first published in 1883 by Osborne Reynolds, is used in
aeronautics and hydraulics for modelling fluid flow2. It is associated with the degree of
smoothness in the flow of a fluid. The slowest flow can be pictured as a series of
parallel layers moving at different velocities (laminar flow). The friction between the 2 Source: www-das.uwyo.edu/~geerts/cwx/notes/chap07/reynolds.html
11
layers gives rise to viscosity. As the fluid flows more rapidly, it reaches a point at which
the viscosity is overcome and the motion changes from laminar to turbulent. There is
chaotic formation of eddy currents and vortices superimposed on the main direction of
flow. It is observed that fluid flow becomes turbulent when Re exceeds about 1400
(open channel flow; Knighton1998). In nearly all naturally flowing systems, the viscous
forces are overcome by the inertial forces and the flow is turbulent. An important
exception occurs in a very narrow laminar layer found running along the surface of the
stream bed (boundaries) as the velocity approaches zero where friction dominates.
Another measure of hydraulic flows is the Froude number (Fr). It was developed by
William Froude (1810-1879), an English engineer and hydrodynamicist who formulated
this reliable law to calculate the resistance water offers to ships and to predict a ship’s
stability in the water. Froude number is used in momentum transfer in general and open
channel flow and wave and surface behaviour calculations in particular. It delineates
between deep slow flow typical of mildly sloping rivers (Fr<1; subcritical) and shallow
rapid flows (Fr>1; supercritical) found in rapids and waterfalls.
In the application of flow hydraulics to spawning research, researchers have described
selected spawning sites as the transitional areas between pools and riffles (otherwise
known as riffle crests or pool tails). Only Moir et al. (1999) quantitatively describe the
transitional areas selected for spawning by using the type of flow described by the
Froude number (Fr). Froude numbers averaging 0.344 were found to be selected by
spawning Atlantic salmon in Scottish streams (Moir et al. 1999). It is within the scope of
this thesis to determine if preferred Re and Fr values for sockeye building redds exist.
At its ideal, water flow should be strong enough to deliver oxygen to and remove waste
materials from redds but weak enough to minimize risk of damage to incubating eggs.
12
The traditional stream habitat measurements of water depth and velocity may be used
to derive the Reynolds and Froude numbers that describe flow types. Research shows
that flow types:
· describe the hydraulic forces on the stream bed or an organism within the
flow (Re; Morisawa 1968);
· affect substratum stability and organisms (Newbury 1996);
· affect available streambed oxygen and survival rates of young salmonids
(Reiser and Bjornn 1979);
· influence required energy expenditures of fishes (Deacon and Hardy 1984 in
Heede and Rinne 1990); and
· influence food delivery and population recruitment (Deacon and Hardy 1984
in Heede and Rinne 1990).
2.1.1 Study area and timeline
Of the 23 km of the Okanagan River accessible to salmon, sockeye spawn primarily in
the remaining 6 km natural reach and 2 km of the channelized reach (Fig. 2.1). The
natural reach begins at McIntyre Dam, the upstream limit to fish migration. This reach is
hydraulically diverse with bars, islands and pools producing a range of water depths
and velocities. The remaining 15 km of river was channelized in the mid-1950’s.
Sockeye are known to spawn in the 2 km reach (channelized reach) running from the
natural reach to Vertical Drop Structure 13 (VDS13) utilizing the gravels that have
accumulated upstream of this VDS. In contrast with varied topography of the natural
reach, the construction of a trapezoidal shaped cross-section in the channelized reach
has created homogenous water depths and velocities.
13
Courtesy of the Okanagan Nation Alliance
Figure 2.1. Okanagan River study area (sites located on the photo inset)
Measurements were taken at redds in the two reaches in October 2002, 2003 and
2004, just after the salmon spawning period peak as well as within four sample grid
sites, which served as the control area for the study. The grid sites measured 30 m by
1
2
3
4Natural reach
Channelized reach
14
12 m. Two grid sites were selected for each reach and measured in 2002 and 2003.
Grid sites were selected based on being representative of the reaches, and all were
known to contain some spawning sites. Sites within the channelized reach were easily
picked since this reach is homogenous. Site 1 was selected near the VDS13 while Site
2 was selected near the top end of the reach. In the natural reach, Site 3 was selected
because it contains an island and a bar, which are features associated with hydraulic
diversity found in much of this reach. Site 4 was selected because it is typical of areas
in the natural reach where sockeye spawn at pool-tail outs (areas that transition from a
pool to a riffle).
2.1.2 Hypothesis and predictions
The purpose of this study is: to determine how flow affects selection of spawning
grounds by salmon (section 3.0); and to evaluate the value of restoring the natural
landscape in channelized reaches (section 4.0). To achieve this, flow types at spawning
sites were identified and measured according to water depth, velocity, Froude numbers
and Reynolds numbers. Then, the availability of these flows in the two reaches where
different types of flows are available was compared.
If certain flow hydraulics, which can be measured as Froude and Reynolds numbers,
are ideal for sockeye salmon spawning sites, then similar measures will be found at
each spawning site surveyed regardless of the broader hydraulic diversity of the site.
The characteristics for water depth and velocity are measured because these variables
are commonly recorded and well documented at spawning sites. Since sockeye
typically spawn in transition areas and the types of flow of these areas can be described
using Froude and Reynolds numbers, I predict that at least one of these variables will
15
be similar at spawning sites selected by Okanagan sockeye in both of the reaches
studied.
If a flow type (e.g. Froude number) is found to be selected for at spawning sites and
since it is a dimensionless quantity, then this flow type should be similar among salmon
species and among different sized rivers. The range of water depth and velocity used
by spawning salmon is well documented, however only Moir et al. (1999) documents
the use of the Froude number by spawning Atlantic salmon in Scottish streams. I
predict that if the Froude number is the variable selected at spawning sites by
Okanagan sockeye salmon that it will be a similar value to Froude numbers
documented in the Scottish study of Atlantic salmon.
If certain flow types are selected for by spawning sockeye salmon are identified, then
the frequencies will be measured and compared at grid sites between the two
hydraulically diverse natural and channelized reaches across time and at differing
discharge levels. In this case, 2002 was a year of average discharge (11 m3/s), and
2003 had lower-than-usual discharges (6 m3/s). I predict that flows in the natural reach
will be more diverse than flows in the channelized reach. I further predict that the
frequency of the ideal flow types will be higher in the natural reach sites. Identifying the
preferred flow types, Froude and/or Reynolds values, and their frequency of occurrence
in both reaches will allow for greater success in riverbed restoration in the channelized
reach section of the Okanagan River as well as other future sockeye habitat restoration
projects.
16
2.2 METHODS
Measurements of water depth, velocity, Froude number and Reynolds number of
spawning sites selected were compared between the two reaches. The water depth, D
in metres (m) and velocity, V, in metres per second (m/s) were measured and Froude
numbers and Reynolds numbers were calculated using D and V measurements.
The Reynolds number is calculated using the mean velocity V, the depth of flow D and
the kinematic viscosity of water, v. Typical values of kinematic viscosity (v) range from
1.8 x10-6 m2/sec for water at 0oC, 1.3 x10-6 m2/sec for water at 10oC and 1 x 10-6 m2/sec
for water at 20oC. Since the water temperatures during spawning are close to 10oC
(between 10 and 15 oC), 1.3 x10-6 m2/sec was used where:
Re = VDν
The Froude number is calculated using V, D and g is the force of gravity (9.81 m/s2)
such that:
Fr = VgD
2.2.1 Redd site measurements
Spawning site characteristics were determined by measuring the undisturbed gravels
approximately 0.5 m upstream of a completed redd. Measurements of water depth and
velocity were taken after peak spawning when fish could often be observed holding
position over their redd and no further digging was observed. No distinction was made
between a functional redd (with eggs inside) and an abandoned redd. Superimposed
redds (when a redd is built over top an existing redd) were avoided. In both years
17
sampling the population did not saturate the spawning grounds so that avoiding redd
superimposition was not a problem.
Immediately upstream of each redd, depth was calculated as the average of three
measurements taken. At each of these measurements sites, average velocities were
recorded. The average velocity of the water depth profile was taken at 60% of the water
depth measuring from the water surface using a velocity meter that recorded averages
over 40 seconds (Appendix 2B). Velocity meters were calibrated and tested periodically
during the study using a Gurley meter.
Redds were measured in October of 2002, 2003 and 2004. In 2002, 15 redds were
measured between the two reaches. This sample size increased in 2003 to 72 redds,
and in 2004 to 127 redds for a total of 214 redds over the three years. In 2004, as part
of a separate study to determine the distribution of redds in the Okanagan River, redd
measurements were made at transects every 200m from McIntyre Dam, (Long 2005).
The same field crew and techniques for measurements were used as in the previous
two years.
The depth and velocity measurements were compared between the natural and
channelized reaches. Additionally, these measurements were used to calculate Froude
and Reynolds numbers. Together these measurements are used to test the first
prediction about which variable(s) is/are descriptive in describing spawning sites
selected.
18
2.2.2 Measurement of available spawning area
Measurements of the depth and velocity of selected spawning sites were compared
with a sub-sample of the depths and velocities available in the two reaches in 2002 and
2003 (Appendix 2C). This was accomplished by setting up a total of four grids within the
two reaches. The two grids (Grid 1 and 2) in the channelized reach were located 16.68
km and 17.65 km, respectively, upstream of Osoyoos Lake. Grids 3 and 4 in the natural
reach were located 18.95 km and 19.15 km upstream of the lake outlet. Grids extended
across the entire width of the river (25 to 30 m) and for 12 m downstream. The grid
consisted of transects 3 m apart with sampling points set every 3m across the river (Fig.
2.2). At each point, water depths (m) and average velocities (m/s) were recorded and
Froude and Reynolds numbers calculated. Grid measurements were completed prior to
spawning (early October) then revisited during (Oct. 16 to 20th) and after spawning (Oct.
28 to 30th) to note where on the grid redds were being built.
Figure 2.2. Example of site photo with a grid overlaid
19
Grid measurements were taken only from sites 2 and 4 in 2002 and from all four sites in
2003. Average flows of 11 m3/s were measured in 2002 while 2003 saw lower than
usual flows (6 m3/s). Average flows were determined from the flows recorded by the
Water Survey of Canada (Okanagan River station 08NM085) between 1944 and 2003
(Fig. 2.3). The sites were chosen as representative of their respective reaches.
Okanagan River f low s
0.0
10.0
20.0
30.0
40.0
50.0
60.0
Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Dis
char
ge (m
3 /s)
mean monthly(1944-2002)2002
2003
Figure 2.3. Okanagan River average monthly flows (Water Survey of Canada)
2.2.3 Statistical analysis
The first study hypothesis investigated site selection by spawning sockeye salmon by
testing which of the variables measured (water depth, velocity, Froude and Reynolds
numbers) were similar between the two reaches. Velocity and Froude number data
were normally distributed and subsequently tested using a Student’s t-test; water depth
and Reynolds number were best analyzed by non-parametric tests (Mann-Whitney test)
due to the non-normal distribution of the data. All tests were considered statistically
significant at α=0.05 (Zar 1999).
Sockeye spawning
20
Because river flows in 2002 were higher than in 2003, Froude numbers were calculated
separately to measure the impact of flow levels. A two factor analysis of variance
(α=0.05) with unequal replication test was run. The factors included were reach and
year, and the variable was the Froude number. An analysis of power was calculated on
parametric tests where no significant differences exist.
2.3 RESULTS
2.3.1 Redd site measurements
The mean water depth measured in the natural and channelized reaches were 0.35 m ±
0.17 m and 0.45 ± 0.12 m, respectively (Table 2.1). These averages are within the
ranges noted in the literature where water depths used by sockeye salmon generally
ranged between 0.15 and 0.77 m (Table 2.2) and those used by Okanagan sockeye for
spawning range between 0.23 and 0.63 m.
Mean velocity recorded in the natural and channelized reaches were 0.54 and 0.68 m/s
respectively (Table 2.1). Again, these results are within the range of values found in the
literature (0.21-1.01 m/s) and in past field studies (0.24-0.85 m/s; Table 2.2).
The average Reynolds numbers of the natural and channelized reaches were 151,913
and 242,324, respectively. The Froude numbers in the two reaches were similar with
average Froude numbers in the natural and channelized reaches of 0.32 and 0.31,
respectively (Table 2.1).
21
Table 2.1. Mean and standard deviations of variables measured at redds in the two
reaches measured in 2002, 2003 and 2004
Reach Sample size
Water depth (m)
Velocity (m/s)
Reynolds no.
(1000’s) Froude no.
Natural 120 0.35 ± 0.17 0.54 ± 0.17 152 ± 103 0.32 ± 0.09
Channelized 94 0.45 ± 0.12 0.68 ± 0.20 243 ± 103 0.31 ± 0.11
Table 2.2. Overview of redd site characteristics of sockeye
Water depth (m)
Average Velocity (m/s) 3
Source
General sockeye site characteristics based on literature reviews
Sockeye spawning preferences 0.3-0.5 0.21-1.01 Long 2000
Sockeye spawning preferences >= 0.15 0.21-1.01 Bjornn and
Reiser 1991; Bell 1986
Sockeye spawning preferences 0.28-0.77 0.45-0.96 Summit 2001
Okanagan sockeye preferences based on field sampling
Field sampling – 1938 and 1939 0.23 0.52 Burner 19514
Field sampling – 1971 0.23-0.46 0.24-0.76 Anon 1973
Field sampling – 1999 0.25-0.63 0.34-0.67 @ 0.1m Summit 2000
Redd distribution 2004 0.25 – 0.59 0.45 – 0.85 Long 2005
Of the variables measured at spawning sites significant differences were found between
the water depth (p<0.001), velocity (p<0.001) and Reynolds numbers (p<0.001). Froude
numbers were the most similar between reaches, p=0.220 suggesting that this variable 3 Average velocities occur at 60% of the depth from the water surface unless otherwise noted. 4 Field sampling completed by Burner (1951) was done prior to the construction of the channel (mid
1950’s) before which sockeye had been documented spawning downstream of Oliver an area used little today by spawning sockeye.
22
best describes site characteristics selected by spawning sockeye. Power of the t-test in
the cases of the null hypothesis being accepted (Froude) and Power = 1 – β, Power
>0.99 ; β <1% . The power of this test is high (power > 0.99) where there is < 1%
chance of making a Type II error5.
2.3.2 Grid surveys
When comparing data for the variables in grids (habitat available) with the areas of the
constructed redds (habitat used), similar patterns emerged. For example, at grid site 4
(natural reach) sockeye were found spawning in areas with Froude numbers of
approximately 0.30 (Fig. 2.4). Little trend was apparent among the other three
characteristics (D, V and Re) analyzed.
When looking only at Froude numbers available at the four grid sites there was a similar
trend. Sites selected for spawning correspond with Froude number ranging between 0.2
and 0.4 (Fig. 2.5).
5 Type II error is the error made if the (null) hypothesis is false but not rejected.
23
4 6 8 10 12 14 16 18 20 22 24 260
2
4
6
8
4 6 8 10 12 14 16 18 20 22 24 260
2
4
6
8
4 6 8 10 12 14 16 18 20 22 24 260
2
4
6
8
4 6 8 10 12 14 16 18 20 22 24 260
2
4
6
8
20000
40000
60000
80000
100000
120000
140000
160000
10
15
20
25
30
35
40
45
a. Water depth (cm)
b. Velocity (m/s)
c. Froude number d. Reynolds Number.
Figure 2.4. Distribution of the variables measured at the Site 4 grid (natural reach
2003).
Transect 3
Key diagram for Figures 2.4 a – d redd locations marked with an X
Transect 1
Transect 2
Transect 4
X XX
X X XX
X X
Numbers on the y-axis denote the distance
upstream of transect 4 in
meters
Numbers on the x-axis denote the distance across the river in meters
X X X
XX X X XX
X X
X X X X
X X X XX X X XX
X X
X XX X X XX
X X
X XX X X XX
X X
X X
Direction of flow
0.5 0.4 0.3 0.2 0.1
1.5
2
2.5
3
3.5
4
4.5
5
5.5
6
24
3 4 5 6 7 8 9 10 11 12 13 14 150
1
2
3
4
5
6
7
8
9
a. Site 1: Channel reach
4 6 8 10 12 14 16 180
2
4
6
8
b. Site 2: Channel reach
4 6 8 10 12 14 16 18 200
2
4
6
c. Site 3: Natural reach
Figure 2.5. Location of redds (X) and distribution of Froude numbers in the remaining grids (2003)
Froude number ranges
X XX
XX XX XXX
X
Direction of flow
X XXX X X
XX X X X
X X X XX X X X X X
X XX XX X
0.5 0.4 0.3 0.2 0.1
25
2.3.3 Measurement of available spawning area in grid sites
Given that of the four variables measured – D, V, Re and Fr – only Fr was found to be
similar between the two reaches, analysis of the available spawning area will be limited
to discussion of the Fr values. The range of Fr numbers in the naturalized reaches was
consistently greater regardless of average or low river discharge (2002, 2003,
respectively) Table 2.3 lists the recorded Froude number ranges for the channelized
and natural reaches for each year studied. It is also worth noting that the range was
larger in 2003 when the river discharge was lower than normal compared to 2002 when
the river discharge was closer to the mean for the season.
Table 2.3. Available Froude numbers in the reaches in the two years sampled
Year Reach Froude No. range
Sample size
2002 Channelized 0.22 – 0.28 19
2002 Natural 0.18 – 0.31 32
2003 Channelized 0.11 – 0.35 31
2003 Natural 0.07 – 0.37 34
The natural reach in both years had a majority of the Froude numbers within the range
selected by spawning sockeye (Fr=0.315 ± 0.10) although there were less diverse flows
in this reach in 2002 (the year of average discharge; Fig. 2.6). In 2003 (the year of low
discharge), the channelized reach contained preferred spawning Froude numbers. In
general Froude numbers available in both reaches were lower in 2002, the year of
average discharge however more diverse in the natural reach.
26
Range of availabile Froude numbers
0
0.05
0.1
0.15
0.2
0.25
0.3
0.35
0.4
0 1 2 3 4 5
Frou
de n
umbe
rs
Figure 2.6. Ranges of Froude numbers available in the two reaches over the two years
studied.
When looking at the differences in available Froude numbers over two discharges and
two reaches a two factor analysis of variance was used. Results of this test reveal that
when α=0.05, there is not a significant effect of the reach on mean Froude numbers
available (p=0.065). There is a significant difference in the mean Froude available
between the two years of differing discharge (p<0.001). Also, there is an interaction of
reach and discharge on available Froude numbers (p=0.007); however, these results
need to be compared to the range of Froude numbers selected for by spawning
sockeye. These comparisons will be discussed in section 2.4.
Natural 2003
Natural 2002
Fr=0.315
Channel 2002
Channel 2003
27
2.4 DISCUSSION
To summarize, the study looked at two geographically diverse regions of the Okanagan
River (channelized and natural reaches) over three years during the sockeye salmon
spawning season to determine if any or all four measured variables – water depth,
water velocity, Froude number, and Reynolds number – could be statistically identified
as significant characteristics at redd sites. The Froude value was the only variable not
found to be statistically different at the redds and therefore similar between reaches.
Areas with Froude numbers of 0.315 ± 0.10 were found to characterize spawning
sockeye areas even though the two studied reaches had varying water depths and
velocities. Grid surveys showed similar trends. Areas used by spawning sockeye had
Froude numbers ranging from 0.2 to 0.4.
These results suggest that past research, which tends to describe typical salmon
spawning areas by water depth and velocity, may be less comprehensive than
previously thought. The nature of redd site selection by salmon is more sophisticated
than generally assumed; salmon select spawning grounds based on the dynamic
characteristic flow. This paper has presented evidence suggesting that the Froude
number, a ratio of gravitational and inertial forces, is a useful characteristic in
determining redd site selection.
At the two study reaches where depths and velocities differed, sockeye were found
spawning within the ranges of depth and velocity documented (Anon 1973; Burner
1951; Bjornn and Reiser 1991; Bell 1986; Long 2005; Summit 2000); however, sockeye
selected spawning sites with specific combinations of water depths and velocities that
only can be described by the Froude number. Shirvell and Dungey (1983) also found
28
that trout prefer spawning areas with specific combinations of depth and velocity more
than either factor alone. Froude numbers 0.2, 0.3 and 0.4, being a function of water
depth and velocity, were plotted on a graph of the depths and velocities found at
spawning sites in the two study reaches (Fig. 2.7).
Spawning selection sites
0.00
0.20
0.40
0.60
0.80
1.00
1.20
1.40
0 0.2 0.4 0.6 0.8 1 1.2
Water depth (m)
Ave
rage
vel
ocity
(m/s
)
Channel Reach
Natural Reach
Froude 0.4
Froude 0.3
Froude 0.2
Figure 2.7. Depths and velocities documented at Okanagan sockeye spawning sites
with Froude numbers 0.2, 0.3 and 0.4 overlaid.
The water depths and velocities found at spawning sites in the two study reaches, for
the most part, fell between Froude numbers of 0.2 and 0.4 even though the water was
frequently deeper in the channelized reach than in the natural reach.
By describing the specific combinations of water depth and velocity, the Froude number
quantitatively describes the flow in the transition zones between pools and riffles, which
in past studies were subjectively identified as spawning areas (Barnard 1992; Briggs
1953; Hazzard 1932; Hobbs 1937; Hunter 1991; Smith 1941; Stuart 1953; Stuart 1954;
29
White 1942). The Froude number is not only a useful single descriptor of the types of
flow at spawning sites but because it is dimensionless it can be compared across
different rivers and fish species (Moir et al. 1999). Dimensionless numbers are
attractive to river dynamics because they are scale-independent. For instance, the flow
in a small tributary creek may be similar to that in the larger main-stem river if certain
ratios are the same.
I predicted that the Froude numbers at spawning sites selected by Okanagan sockeye
salmon and Atlantic salmon in Scotland would be similar. Froude numbers found at
spawning sites in Scotland average 0.344 (Moir et al. 1999). Compared to the
sockeye’s spawning sites, whose Froude numbers are 0.315 ± 0.10, Moir’s calculations
were found to be significantly different (two-tailed one sample hypothesis t-test with
α=0.05). This was unexpected since their ranges overlap considerably (Fig. 2.8). The
difference may be because both sets of data represent habitat utilization, that is the
areas that spawning salmon were found to use. Because habitat utilization is a function
of availability and preference, both of which were not taken into account (Moir et al.
1999), it could be that either the Froude numbers available in the Okanagan and the
Scottish system differ or that the habitat preference of sockeye or Atlantic salmon differ
thereby affecting utilization.
30
00.05
0.10.15
0.20.25
0.30.35
0.40.45
0.5
Scottish Atlanticsalmon
Okanagan sockeyesalmon
Frou
de n
umbe
rs
Figure 2.8. Ranges and means of Froude numbers documented for spawning Atlantic
and sockeye salmon.
Addressing the third prediction, differences in Froude numbers available spatially (inter-
reach) and temporally (inter-annual) were investigated. Froude numbers available in the
reaches studied vary with changes in the discharge or amount of flow because at
greater discharges the water depths will increase and velocities will change depending
on the confinement of the channel. I predicted that the natural reach had more diverse
flows providing suitable spawning areas for sockeye at both average and low discharge
levels. The natural reach did have a slightly greater range of Froude numbers available
in both years studied mostly likely due to the hydraulic diversity created with bars,
islands and pools that produce a range of water depths and velocities, which contrast to
the homogenous water depths and velocities found in the trapezoidal-shaped cross-
section of the channelized reach. It is interesting to note that the low discharge levels
produced a greater range of Froude numbers than those found in the years of average
discharge but the fewest selected Froude numbers in the channelized reach.
31
Although there is a wider range of Froude numbers available in the natural reach in
both years compared to the channelized reach, the two ranges were not found to be
significantly different (p=0.065); however this may be due to the sampling method.
Using two grid survey sites in the channelized reach most likely covered the range of
water depths and velocities due to its hydraulically homogenous nature, whereas
selecting two sites in the hydraulically diverse natural reach, although representative of
typical spawning areas did not encompass the entire range found within the reach6.
A greater range of Froude numbers is beneficial because it increases the chance that
Froude numbers preferred by spawning salmon will be present at different discharges
(inter-annually). Thus, a streambed with greater Froude number diversity will create
greater salmon population stability because fluctuating discharge levels will have a less-
significant impact on spawning success. Different discharges may change which
sections of the riverbed have preferred Froude numbers, and this may explain why
salmon are found choosing new spawning locations in years of different flows (Thurlow
and King 1994).
In conclusion, the results of this Okanagan River survey indicate that flow plays a role in
where and how sockeye salmon choose to build redds and spawn. Specifically, by
measuring the relationship between the gravitational and inertial forces – the Froude
number – it is possible to determine if a streambed is suitable for spawning. The flow of
water assists the salmon by easing movement of gravels during redd construction thus
ensuring the salmon build nests that are most favourable for egg maturation. Even the
6 Given the confines of time and available resources as well as potential environmental damage to the
spawning grounds, it would be unreasonable to do an exhaustive study of the entire natural reach.
32
placement of the eggs is determined, in part, by water flow. Flow also creates a
sustainable environment for eggs during the vulnerable incubation period because the
movement of the water through the eggs provides the necessary oxygen whilst
simultaneously flushing out waste materials, which is discussed further in next chapter.
The little things, the seemingly immeasurable things, have time and time again shown
themselves to be factors that can differentiate between life and death, success and
failure. Not all of them can be measured or predicted. In the case of this study,
however, we have gained a small piece of information to help us understand the
sockeye salmon spawning process. Geographically diverse areas can be equally
suitable for spawning if the relationships between gravitational and inertial forces are
similar. Finally, given that these findings about flow are similar to other findings, notably
Moir et al.’s study on Atlantic salmon in Scottish rivers, this study contributes to a
growing body of knowledge that could impact not only the community’s understanding
of the factors affecting spawning but also how environmental restoration should be
approached.
33
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US Forest Service, Pacific Northwest Forest Range Exp. Station General Technical
Report PNW-96. 54pp.
Shirvell, C.S. and R.G. Dungey. 1983. Microhabitats chosen by brown trout for feeding
and spawning in rivers. Trans. Am. Fish. Soc. 112:355-367.
Smith, A.K. 1973. Development and application of spawning velocity and depth criteria
for Oregon salmonids. Trans. Am. Fish. Soc. 102:312-316.
Smith, O.R. 1941. The spawning habits of cutthroat and eastern brook trout. J. Wildlife
Management, 5(4):461-471.
Stuart, T.A. 1953. Water currents through permeable gravels and their significance to
spawning salmonids. Nature. p407-408.
Stuart, T.A. 1954. Spawning sites of trout. Nature. 173:345.
Summit Environmental Consultants Ltd. (Summit). 2000. Okanagan River sockeye
spawning habitat assessment. Prepared for Okanagan Nation Fisheries
Commission, Westbank, BC.
Summit Environmental Consultants Ltd. (Summit). 2001. 2000 Okanagan River
sockeye spawning habitat assessment. Prepared for Okanagan Nation Fisheries
Commission, Westbank, BC.
Summit Environmental Consultants Ltd. (Summit). 2003. A review of geomorphic and
hydraulic factors controlling the distribution, abundance and quality of sockeye
salmon habitat in the Okanagan Basin from 1900 to present. Prepared for
Okanagan Nation Fisheries Commission, Westbank, BC.
Tautz, A.F. and C. Groot. 1975. Spawning behaviour of chum salmon and rainbow
trout. J. Fish. Res. Board Can. 32:633-642.
39
Thurlow, R.F. and J.G. King. 1994. Attributes of Yellowstone cutthroat trout redds in a
tributary of the Snake River, Idaho. Trans. Am. Fish. Soc. 123:37-50.
WSC. 2004. Water Survey of Canada real-time hydrometric data
http://scitech.pyr.ec.gc.ca/waterweb
Webster, D.A. and G. Eiriksdottir. 1976. Upwelling water as a factor influencing choice
of spawning sites by brook trout (S. fontinalis). Trans. Am. Fish. Soc. 3:416-421.
White, H.C. 1942. Atlantic salmon redds and artificial spawning beds. J. Fish. Res. Bd.
Canada. 6(1):37-44.
Witzel, L.D. and H.R. MacCrimmon. 1983. Redd-sites selection by brook trout and
brown trout in Southwestern Ontario streams. Trans. Am. Fish. Soc. 112:760-771.
Wood, C.C. 1995. Life history variation and population structure in sockeye salmon.
American Fisheries Society Symposium. 17:195-216.
Zar, J.H. 1999. Biostatistical analysis. Fourth edition. Prentice-Hall, New Jersey.
Zimmerman, A.E. and M. Lapointe. 2005. Intergranular flow velocity through salmonid
redds: sensitivity to fines infiltration from low intensity sediment transport events.
River Research and applications. 21: 865-881.
40
3.0 OKANAGAN SOCKEYE EGG SURVIVAL
3.1 INTRODUCTION
For humans, playing an Al Green song may create an environment that is conducive to
procreation; however, Al Green songs are not a necessary condition for the successful
gestation of embryos. Like humans, the requirements that salmon need for successful
spawning are different from the conditions for successful incubation of eggs. Unlike
humans, however, once the eggs are fertilized there is no further connection between
the eggs and either parent. The eggs must mature in the nest, or redd, where they were
deposited shortly after fertilization. The conditions of spawning, therefore, are
inextricably linked to the conditions of incubation even though the habitat requirements
of incubating embryos are different from those of spawning adults (Bjornn and Reiser
1991).
During the incubation period, the survival of fertile embryos is determined by the
environment within each redd, which must provide sufficient aeration and inter-gravel
space (Chapman 1988; Lisle 1989; Quinn and Foote 1994). Redds are constructed in
gravel substrate through a combination of tail movements by the salmon (Burner 1951;
Chapman 1988; Fabricus & Gustafson 1954; Hart 1973 in Pauley et al 1989; Hobbs
1937; Jones 1960; Kondolf et al. 1993; Mathisen 1955 in Forester 1968; McCart 1969;
Needham 1961; White 1942; Young, et al. 1989). Although salmon are described as
digging redds, their undulating tail movements against the substrate are used to create
a suction force7 that lifts the bed material up into the flow. Once exposed to the flow
above the bed, gravel particles are carried downstream and deposited to form a
7 Digging increases the local shear stress by creating higher near-bed velocities and turbulence.
41
hummock or mound on the rivers bed. Finer fractions of sediment are suspended in the
water column and swept much further downstream (Kondolf et al. 1993). Particles too
large to be moved by the fish remain behind in the trough as a coarse lag creating
interstices that make excellent sites for the lodgement of eggs after which they are
covered with more gravel by the same ‘digging’ process (Burner 1951; Hobbs 1937).
When complete, redds constructed in running waters are oblong shaped with their long
axis parallel to the current (McCart 1969). The upstream face is sloped with the
uppermost egg pocket generally located beneath this face forming a hummock or
mound that precedes a trough (Fig. 3.1). Within the hummock three to ten nesting
pockets lie, each with 750 eggs on average (Hart 1973 in Pauley et al 1989). The
successfully built redd creates a suitable incubation environment for the eggs to survive
until ready to emerge.
Figure 3.1. Salmon redd profile showing multiple egg pockets; White 1942
42
The redd environment is maintained by interstitial water flowing past individual eggs. A
positive correlation has been documented between water flow – measured as velocity –
within a redd and egg incubation survival (Alderdice et al. 1958; Chapman 1988; Coble
1961; Reiser and Bjornn 1979; Shumway et al 1964; Wickett 1954). Although in the
previous section (2.0), flow was measured as a relationship between inertial,
gravitational and viscous forces (Froude and Reynolds numbers), in the case of
groundwater flow the dominating factor is the force of friction as water flows through the
bed substrate. This friction-dominated flow creates water velocities that are a small
fraction of those in the water column above the substrate and may vary greatly among
nests and even between eggs (Cooper 1965). Water velocity through a redd is the
primary variable for oxygen delivery to the embryos and simultaneous removal of
metabolic wastes from the redd (Chapman 1988; McBain and Trush 1999; Silver et al.
1963).
The two factors most commonly documented as detrimental to egg survival in redds are
both factors of inadequate flow. They are fine sediment deposition (Argent and Flebbe
1999; Bams 1969; Bjornn and Reiser 1991; Dill and Northcote 1970; Koski 1966) and
insufficient inter-gravel dissolved oxygen (IDO) (Wood 1995; Pauley et al 1989; Bams
1969; Emmette et al. 1992; Brannon 1965; Peterson and Quinn 1996), which is often
the result of the former. Although accumulated fine sediment (f%) can impede water
flow and thus the amount of oxygen (IDO) carried to incubating eggs, according to
Darcy’s Law – a function that describes the rate at which water flows through porous
media – fines are only one of several factors affecting the flow of water through
substrate. Zimmerman and Lapointe (2005) used Darcy’s Law to calculate the inter-
gravel flow at the redd-scale (Fig. 3.2).
43
Figure 3.2. Multi-scale processes potentially controlling intergravel flow near redds
(Zimmerman and Lapointe 2005)
Darcy’s Law is named after Henry Darcy of Dijon, France, who formulated it in 1856
after conducting extensive research on how water flows through sand filter beds8.
Darcy’s Law is most often used to describe flow through an aquifer. It is a function of
hydraulic conductivity, which measures the ease with which water flows through a
sediment or substrate matrix, and the force of gravity, expressed as a hydraulic gradient
from a higher to a lower water level. Using Darcy’s Law the velocity of flow through the
bed substrate (Vg), can be calculated as the product of hydraulic conductivity, K, and
hydraulic gradient, (h1-h2)/d (Knighton 1998). Hydraulic gradient is a ratio of headloss
(h1-h2) – or differences in the height of water between two points – and length of the
flow path (d). The groundwater flow velocity proposed by Darcy is:
8 http://sis.agr.gc.ca/cansis/glossary/darcys_law.html
44
Hydraulic conductivity (K) measures the ease of moving water through a porous
medium (Mays 2001), where the ease of water movement is determined by the
composition and characteristics of the substrate medium. The hydraulic conductivity of
the variety of substrate types (i.e. silty sand, clean sand, gravel) have been
experimented on and are well documented (Davis and DeWeist 1966). For example,
the amount of fine sediment within the gravel decreases the hydraulic conductivity
causing the inter-gravel water flow supplying eggs with oxygen to become
compromised (Montgomery et al. 1996; Reiser and White 1981;Tagart 1984). This was
the case for Harrison (1923) whose documentation of low survival of sockeye fry with
increased fine sediment loading remains a benchmark study.
Hydraulic gradient like the stream gradient is calculated as the change in the water
surface elevation over the distance covered. Although hydraulic gradient is typically
measured to describe the movement of water through an aquifer (groundwater flow), in
this study the redd steepness – or gradient of the redd profile - over the two metre long
redd was measured. This redd steepness value was suitable because the redd’s profile
in the water column creates the hydraulic gradient seen in a dip in the surface of the
water. In the study of flow supply to incubating eggs the hydraulic gradient of the redd
has generally been overlooked as a factor affecting flow, yet it is an important factor
describing down-welling flow9 through a porous medium. Studies on the size of redds
built by salmon documented that redd size is known to vary in direct proportion to the
size of the salmon (Thurlow and King 1994; Burner 1951), however these results looked 9 Down-welling refers to the overall movement of stream water down through the substrate opposed to a
spring which occurs as groundwater flows up from the substrate.
45
at the surface area of the redd (m2) and not the height, or gradient of the redd’s profile,
or the resulting hydraulic gradient.
Although measurements of hydraulic gradient and redd steepness have been largely
overlooked, it is generally accepted that the redd’s profile is known to induce down-
welling currents through the gravel (Cooper 1965; Kondolf 1988; Chapman 1988;
Zimmerman and Lapointe 2005). Furthermore, it has been suggested, that variability in
the shapes of redds may be an attributing factor to variability in dissolved oxygen
delivery in redds (Ringler and Hall 1975 in Thurlow and King 1994). A well-defined flow
of water beneath the riverbed at redd sites was also described by Stuart (1953) and
demonstrated by Cooper (1965) in laboratory flumes. Cooper (1965) found that the
presence of a redd drew surface water deeper (Fig. 3.3) than water flowing over a flat
gravel bed (Fig. 3.4).
Figure 3.3. Flow paths through homogenous gravel with a surface similar to a redd
(Cooper 1965)
46
Figure 3.4 Flow paths through homogenous gravel with a level gravel surface (Cooper
1965)
In the present study, the accumulation of fines and the redd steepness are used to
make inferences on the potential amount of flow passing through a sockeye salmon
redd and relate this flow to the survival of pre-hatch eggs in two hydraulically diverse
reaches of the Okanagan River. This was accomplished by measuring in both reaches:
(1) egg survival and inter-gravel dissolved oxygen (IDO) in artificial redds; (2) percent
fine accumulation in the redd hummock materials; and (3) the redd steepness created
by measuring the shape or profile of the redd.
3.1.1 Study area and timeline
Of the 23 km of the Okanagan River accessible to salmon, sockeye spawn primarily in
the 6 km natural reach and 2 km of the channelized reach (Fig. 3.5). The unmodified
natural reach begins at McIntyre Dam, the upstream limit to fish migration. This reach is
hydraulically diverse with bars, islands and pools producing a range of water depths
and velocities. The remaining 15 km of river was channelized in the mid-1950’s
47
Sockeye are known to spawn in 2 km of the channelized reach that runs from the
natural reach to Vertical Drop Structure 13 (VDS13) because a weir catches the gravel
and allows it to accumulate upstream of this VDS. In contrast with the varied
topography of the natural reach, the construction of a trapezoidal shaped cross-section
in the channelized reach creates homogenous water depths and velocities.
Figure 3.5. Okanagan River profile identifying the reaches and sites 1 through 4
Egg survival was investigated in both the natural and channelized reaches of the
Okanagan River. Within each reach two sites were selected based on areas where
sockeye were known to spawn and each site was representative of their respective
reach. Egg baskets were placed in artificial redds at each site (sites 1 – 4)10. Sites
within the channelized reach were easily picked since this reach is homogenous. Site 1
was near VDS13 and Site 2 was near the top end of the reach. In the natural reach,
10 Sites 1-4 correspond with grid sites from section 2.0
270
275
280
285
290
295
300
305
310
315
320
325
330
0 2 4 6 8 10 12 14 16 18 20 22 24 26 28
Di st a nc e f r om Osoy oos La k e ( k m)
Osoyoos Lake
McIntyre Dam
Channelized Reach
Natural Reach 4
3
21
48
Site 3 was selected because it contains an island and a bar, which are features
associated with hydraulic diversity found in much of this reach. Site 4 was selected
because it is typical of areas in the natural reach where sockeye spawn at pool tail-outs.
Pool tail-outs are areas that transition from a pool to a riffle.
Given that this was a multi-year study, the methodology was adjusted as data was
collected and analysed. This allowed for errors to be corrected, such as problems
setting the control variables, as well as new research and ideas to be incorporated into
the study. The analysis of the effects of redd steepness on the potential inter-gravel
flow, for example, only was introduced after data from the first year was collected.
Research identified it as a means for explaining differences observed in egg survivals,
the redd steepness and the amounts of fines accumulated.
Egg baskets were placed during October of 2002 and 2003 in both the natural and
channelized reaches. This study specifically focuses on pre-hatch incubation survival
which occurs between October and December because this is a critical stage during
incubation and is known to have a high mortality rate (MacKenzie and Moring 1988 in
Argent and Flebbe 1999). In 2002, IDO was measured in artificial and natural redds but
this was discontinued because levels observed were generally within the range
considered optimal for egg survival thereby suggesting IDO was not affecting egg
survival rates at these sites.
The percent fines accumulated and gravel composition was measured from the
incubation basket environment in 2003. Redd steepness was calculated at each of the
artificial redds and compared with 37 redds built by sockeye in the two reaches. These
49
redds were measured in both reaches in October 2002 and 2003, just after the salmon
spawning period peaks.
Artificial redds were located in areas where sockeye were known to spawn and later
were determined to be where preferred Froude numbers (Fr=0.315 ± 0.10) were found.
The redds built by sockeye were those closest to the artificial redds and the same redds
that were measured in section 2.0 have these preferred flows.
3.1.2 Hypothesis and predictions
The goals of this project are: (1) to estimate pre-hatch egg survival (i.e. mean and
range) for sockeye salmon incubating in two hydraulically different reaches – natural
and channelized – of the Okanagan River; and (2) to explore the relationship between
the egg survival and the potential flow passing through a sockeye salmon redd.
Since section 2.0 identified that Okanagan sockeye select spawning sites with similar
types of flow, specifically measured as the Froude number (Fr), regardless of other
hydraulically diverse characteristics at the sites, then it is speculated that egg survivals
in redds built at these sites should be similar regardless of their location in the natural or
channelized reaches. Therefore, I predict that egg survival and IDO levels, are not
significantly different in redds selected in either reach since the sites were selected by
sockeye salmon based on similar Froude numbers (Fr=0.315 ± 0.10).
Based on previous studies of egg survival, it is expected that there will be high amounts
of variability in these survival results (Bardonnet and Bagliniére 2000; Cunjak et al.
2002). I hypothesize that some of the variability in egg survival can be explained by
relating variations in survival to the variations in the fine sediment accumulation and
50
redd steepness. I predict that combinations of high amounts of fine sediment and/or low
redd steepness will potentially reduce the amounts of flow through the redd, therefore
explaining some of the lower egg survival rates.
3.2 METHODS
To determine egg survival in the two reaches, survival rates were measured from
incubation baskets in artificial redds placed at two representative sites in each of the
reaches. IDO was also measured in the artificial redds as well as in redds built by
sockeye in both reaches. Similarly to the work done by Zimmerman and Lapointe
(2005), based on Darcy’s Law, inferences on the amount of water passing through
salmon redds by (1) measuring fine sediment accumulation and gravel composition;
and (2) redd steepness created by measuring the shape, or profile, of the redd.
3.2.1 Egg survival
Incubation baskets like the ones used in this study (Fig. 3.6) have been used by
researchers to study developing eggs in France, Sweden, Scotland, the United States
and Canada. This style of incubation basket has been used for species such as Atlantic
salmon, brown trout, brook trout, grayling, and all five Pacific salmonids (Bardonnet and
Gaudin 1990; Bardonnet et al. 1993; Cunjak et al. 2002; Flanagan 2003; Harshbarger
and Porter 1979, MacCrimmon et al. 1989; Rubin 1995; Scrivener 1988).
51
Figure 3.6. Incubation basket as it is placed within the substrate (Flanagan 2003).
The primary advantage of using an incubation basket is the ability to start with a known
number of eggs. Because of this, an accurate estimate of survival can be made. These
incubation baskets also collect fine sediment, which can offer insight into the survival
rate within a given basket. The disadvantages of incubation baskets are their
susceptibility to loss or displacement because they are buried rather than anchored in
the gravel and it is only assumed that they accurately simulate the incubation
environment of natural redds. Overall, incubation baskets are found to be suitable
surrogate nesting environments for salmon. Flanagan (2003) evaluated the potential
effects of the incubation baskets on the survival of eggs to emergence and found that
eggs reared in the incubation baskets in a fish hatchery had an excellent survival rate
(S=98%) and no adverse impact on egg development. . The inclusion of incubation
baskets in this study allows for difficult variables to be measured (e.g. percent fines) as
well as controls to be set (e.g. initial number of eggs deposited) .
Incubation baskets (as described in Bardonnet and Gaudin, 1989; and Cunjak et al.
2002) are cylindrical in shape, constructed of white PVC pipe-fitted caps (10.2 cm
52
diameter) for the top and bottom of the basket. White Nytex screening (2 mm mesh
openings), bonded along the seam with silicone sealant, make up the 35 cm long
cylinders. The percent of the surface (mesh) exposed to gravel is 40% of the basket
(Flanagan 2003).
Sockeye eggs were collected from wild fish caught as part of the Okanagan Nation
Alliance Fisheries Department’s (ONAFD) broodstock program which collects sockeye
eggs for incubation in a hatchery. The Shuswap Hatchery staff was on site during
broodstock collection which was in accordance with the Alaska Protocol (McDaniels et
al 1994; S. Wolski11). In 2003, the eggs from several females were pooled and fertilized
by at least two males, mixed, then divided into batches of 100 eggs and placed in sterile
dry bottles for transfer to artificial redd sites. Bottles were stored in a cooler and kept
within 2o C of the river temperature. Eggs were collected in the field but not fertilized
until just before placement in incubation baskets. The time elapsed between extracting
the eggs and having them set in artificial redds was ≤4 hours. Six baskets were placed
at each of the four sites.
Similar methods were used in 2002 except 10 incubation baskets were placed in each
study site and sockeye eggs were collected by ONAFD technicians gillnetting with 10
cm sized mesh of standard gang mono-filament netting (10m long by 10m deep). Fish
capture occurred mostly upstream of site 4, within the natural reach where the fish
congregated. Fish were spawned on site by technicians who were trained by hatchery
personnel. Ten ripe females were spawned into a clean, dry and sterilized tub. Five
males were then tested for ripeness before adding their milt to the eggs. Fertilized eggs
11 Wolski, S. Manager, Shuswap Hatchery, Lumby BC. personal communication. October 15, 2003
53
were counted into sterile dry bottles (100 fertilized eggs per bottle). These bottles were
again stored in a cooler with river water and temperatures were kept within 2o C of the
river temperature. Eggs were placed into incubation baskets within eight hours of fish
capture. Salmon eggs held for longer periods (up to 48 hours) lose their ability to be
fertilized (S. Wolski12).
Incubation baskets were seeded with eggs and placed in artificial redds on Oct. 11th
and 15th in 2002 and Oct 10th, 17th and 20th in 2003. Control baskets also were prepared
in both years. Control baskets are incubation baskets prepared the same way, seeded
with the same batch of eggs, and kept at sites 3 and 4 under similar conditions as the
incubation baskets. Control groups were set up at the redd sites, noted above, and a
control group at the hatchery. Control baskets were retrieved and the eggs were
checked for notochord development after 150 Accumulated Thermal Units, which was
usually 10 to 15 days after fertilization using the vinegar technique13. The numbers of
live eggs (notochords present) from control baskets were compared to survival rates
tabulated by the Shuswap Hatchery in December 2003. Hatchery survival rates were
noted from the same batch of eggs that incubation baskets were seeded with but
incubated in the hatchery control groups. The results of on-site controls and hatchery-
raised eggs were used to correct the survival of eggs in baskets by accounting for egg
viability and the success of fertilization (Appendix 3A). In cases where an on-site control
was used along with hatchery controls from the same batch of eggs, an average of all
controls was used for that batch. In 2002, the two control baskets had 75% (site 4,
seeded Oct. 11th) and 20% (site 4, seeded Oct. 15th) fertilization survivals. In 2003, the
12 Wolski, S. Manager, Shuswap Hatchery, Lumby BC. personal communication. October 15, 2003 13 Seimens, M. Manager, Summerland Trout Hatchery Summerland, BC. personal communication, October
5, 2002). The vinegar technique: by soaking salmon eggs in vinegar only days after fertilization is suspected, the notochord becomes opaque in the translucent egg and a present notochord verifies that the egg has been fertilized and is beginning to develop.
54
fertilization success was 0% (site 3, seeded Oct. 10th), 87% (below site 1, seeded Oct.
17th) and 96% (site 4, seeded Oct. 20th). The hatchery survivals, recorded December
2003, were 72% (hatchery tray 47-62), 84% (tray 35-37) and 94% (tray 38-40).
Egg survival in artificial redds in 2002 was below the expected range14 possibly
because of poor spawning techniques (i.e. controls containing as low as 20%
fertilization success) and/or a lack of a hatchery control to test survival over the
incubation period as was done in 2003. Seeded incubation baskets were placed in
artificial redds at sites where wild sockeye salmon are known to spawn based on past
spawner surveys (Long 2001; Lawrence and Alex 2003; Summit 2001, 2003). At each
site, local gravel was sieved with 2.5 cm mesh and placed in each incubation basket.
Fertilized eggs were introduced into the baskets within the gravel matrix using a funnel
and plastic tube to ensure eggs were dispersed within interstitial gravel spaces in order
to maintain low egg densities and to lessen the probability of eggs being damaged
during installation. Baskets were then topped up with gravel and capped and placed
within artificial redds. To prevent the risk of density dependent mortality, which is
mortality arising from an increased demand for oxygen due to a greater concentration of
eggs (Wickett 1958), only densities of 100 eggs per 2860 cm3 was use. This density is
well below recommended densities of 30 eggs per 108 cm3 (Rubin 1995).
Artificial redds were dug 30 cm deep in an area of approximately one square metre.
Baskets were arranged at a 45o angle in the pit with the screw lid top facing
downstream. The baskets then were covered from the upstream side with clean sieved
14 Hyatt, K. Head Salmon in Regional Ecosystems Program, Science Branch Fisheries and Oceans
Canada, Pacific Biological Station, Nanaimo, BC. personal communication, Email March 11, 2004.
55
gravel to avoid the chance of fines being introduced into the basket. Only a portion of
the basket lid was left exposed.
Egg incubation usually lasts 50 to 140 days (Scott and Crossman 1973); sockeye
embryos hatch between December and February. After hatching, the alevins remain in
the gravel before emerging as free-swimming fry, which happens between March and
May (Shepard and Inkster 1995; Long 2002; Lawrence 2003). In 2002, half of the
baskets were pulled from the artificial redds at hatch (January) and the others were
monitored during emergence (April and May; Appendix 3B). In 2002, it was determined
that majority of the die-off had occurred at hatch since similar survivals were seen after
hatch and during emergence. In 2003, therefore, the baskets were pulled during pre-
hatch, allowing for only one and two month incubation periods (November 2003 and
December 2003, respectively)15. Incubation baskets were removed from their artificial
redds simply by pulling them out. A bucket was placed below the basket as soon as it
was retrieved from the redd in order to collect all the sediment that had accumulated
within the basket. Once the basket was retrieved, the contents were separated to count
live and dead eggs; gravel was sieved from the accumulated fines. The displacement
volume of gravel placed inside the basket (> 2 mm) was measured along with the
measurement of each piece’s b-axis. The b-axis is neither the largest or smallest
diameter of the gravel and therefore it represents the average substrate diameter. Fine
sediment (<2 mm) was bagged on site for drying and sieving in the lab (section 3.2.3) 16.
15 Differences in egg survival were not due to inter-gravel predation. Invertebrates found within the traps
when they were retrieved were identified and later their status as a predator of salmon eggs was determined (D. Craig, personal communication, March 1, 2004). If these predator invertebrates were affecting egg survival then we should see decreased survivals in baskets with the greatest number of these invertebrates. This was not the case; the bulk of predatory invertebrates (Appendix 3C) were found in the natural reach where the survivals were highest therefore not affecting the survival rate of eggs within baskets.
16 Sub-surface water temperatures were measured in the baskets and compared to water surface temperatures to see if there were warmer sub-surface flows at sites where the baskets were placed
56
The median size of the diameter of the gravel both within the incubation baskets and
those in hummocks built by sockeye were measured to determine if the gravel matrix
inside the incubation baskets was representative of the matrix in hummocks in both the
natural and channelized reaches. All of the gravel placed in the incubation baskets was
measured. In each of the 41 natural redd hummocks measured in the two reaches, 24
particles of gravel were collected from the top of the hummock. Substrate sizes were
measured using calipers along the b-axis (i.e. neither the longest nor the shortest). In
order to determine if the gravel sizes in artificial and sockeye built redds were similar,
the D50 (or median of the 24 samples from each basket or hummock) was compared
using a Mann-Whitney test statistic. This non-parametric test was chosen because of
the non-normal distribution of the 41 sockeye built and 24 artificial redd substrate
measured. The median substrate was 30 mm and is within the normal range for
spawning sockeye (2 to 64 mm; Cope 1996).
The percent survival for each basket is recorded as survival (S, as a %) to pre-hatch
and is calculated as:
where n is the number of live eggs (or emergent fry for 2002) enumerated upon retrieval
of basket; i equals the initial number of eggs placed in basket (e.g. i = 100); and m is
the number of dead eggs in hatchery/control group (Cunjak et al. 2002). The survival
values (S%) were tested for statistical difference between the two reaches using a two
indicating a spring present and therefore an additional factor that drives egg survival. No fluctuations were found.
57
sample t-test (α = 0.05; Zar 1999). The data was assumed to be normal and
homogeneous.
Egg incubation and emergence survival data measured in 2002 were not used in the
analysis because of the atypically low survival rate, likely due to poor fertilization
techniques, and no hatchery control to correct for egg survival (redundant) from factors
such as handling and/or fertilization success. In 2002, almost no survival in the
channelized reach was noted and in the natural reach only low survivals ranging 4.72 ±
5.66% were found at both hatch and emergence.
3.2.2 Inter-gravel Dissolved Oxygen (IDO)
Since there is a direct relationship between egg survival and the amount of IDO (Wood
1995; Pauley et al 1989; Bams 1969; Emmette et al. 1992; Brannon 1965; Peterson
and Quinn 1996) then areas with the highest IDO should contain some of the greatest
egg incubation survival. Dissolved oxygen (mg/l) was recorded at a depth of 20 cm
within both the incubation baskets and the natural redds of both reaches. The depth of
the probe was located at the depths sockeye egg pockets were found. The mean
deposition depth of the uppermost egg(s) of Okanagan sockeye is 0.08 m (Rebellato et
al. 2003). IDO measurements were collected using a metal probe (Fig. 3.7) to extract
and transfer the water into a receptacle for measurement by the oxyGuard (Beta model)
dissolved oxygen meter. For the first year of the study (2002), IDO was measured
during spawning (October 2002), hatch (January 2003), and post-hatch (February
2003) at each of the 39 artificial redds and at the 40 redds sockeye-built in both
reaches. Since IDO levels were not low enough to negatively impact egg survival
measurements were not continued during the 2003 egg survival sampling.
58
Figure 3.7. DO extracting vet probe and Oxyguard meter.
3.2.3 Redd substrate measurements
The levels of IDO reaching incubating eggs is known to vary indirectly with the amount
of fines that accumulate in spawning redds (Chapman 1988) because fines tend to
reduce the hydraulic conductivity or gravel permeability which affects delivery of IDO
(Alderdice et al. 1958; Barnard 1992; McNeill and Ahnell 1964; Reiser and Bjornn 1979;
Scrivener and Brownlee 1989; Wickett 1958). However the amount of accumulating fine
sediment is only one component affecting the hydraulic conductivity or the rate at which
water can penetrate or pass through the substrate of the redd. Because hydraulic
conductivity, K, depends on the characteristics of the medium, the proportion of fine
sediment (< 2 mm) within the gravel matrix was measured in artificial redd baskets to
simulate the hummock environment where eggs typically lie.
59
The median size of gravel placed in the incubation baskets was established17 both
within the incubation baskets and in hummocks built by sockeye. Median gravel sizes in
the naturally occurring hummocks were measured and compared to incubation baskets
in order to determine if the gravel matrix inside the incubation baskets was
representative of the matrix in hummocks in both the natural and channelized reaches.
Accumulated fine sediments including sand (≥1 mm) and fines (<1 mm)collected from
each incubation basket were completely dried then sorted using sieves of the following
sizes; 2 mm, 1 mm, 0.5 mm, 0.25 mm, 0.15 mm, 0.037 mm and a pan to catch the
remaining <0.037 mm particles. With sieves stacked in descending order, they were
placed in a sediment shaker18. They were shaken for nine minutes to separate particles
into the size fractions mentioned above. Sorted sediment was weighed (± 0.01 g) in
order to determine the percentage of fine sediments by weight.
The volume of accumulated fines was measured by liquid displacement in a graduated
cylinder and then compared with the displacement volume of the gravel substrate and
the volume of the basket to determine what percent of the basket’s volume was
available to be filled by fines. Since egg survival depends on inter-gravel flow, the
permeability (Chapman 1988) – or the interstitial spaces within the gravel – is a key
component of suitable incubation habitat. Therefore, the amount of fines (f%) in terms
of the available space within the artificial redd (basket) was measured. This was
accomplished using the equation (Flanagan 2003):
17 Detailed methods found in section 3.2.1 18 Rainhart Co. Laboratory Sifter. Pat. No. 3521750 Cat. No. 687 supplied by the British Columbia Ministry
of Transport and Highways
60
Where vol fines is the volume of the fines (< 2 mm), vol bsk is the volume of the incubation
basket (2860cm3); and vol sub is the volume of the initial substrate placed in the
basket19. This calculation measures the amount of space available to the eggs within
the substrate matrix and subsequently what percentage of that space was eliminated
due to accumulated fines. The percent fines (f%) were tested for significance between
reaches using a Student t-test (α = 0.05; Zar 1999).
3.2.3 Redd steepness measurements
The hydraulic gradient is the drop in hydraulic head per unit distance in the direction of
the stream flow (Davis and DeWeist 1966; Hauer and Lambert 1996), in other words
the drop in height of the water surface between two points. The amount of hydraulic
gradient is produced in part by the redd steepness created by the fish building the redd
(Fig. 3.8). The redd steepness created by the fish is the change in elevation of the bed
between the depth of the trough and height of the hummock of a redd. Redd steepness
was also measured to determine if artificial redds were representative of redds built by
Okanagan sockeye. Zimmerman and Lapointe (2005) investigated flow in salmon redds
but caution that “the flow path of water through the redds has not been observed and
thus it cannot be definitively confirmed that redd-scale circulation drives inter-gravel
flow through redds”. This is an important cautionary note given the untested assumption
that degrees of redd steepness will create similar patterns of hydraulic gradient driving
inter-gravel flow.
19 The volume of fines was not measured in 2002 therefore the amount of accumulated fines could not be
calculated that year.
61
Figure 3.8. Redd profile showing the relation between the hydraulic gradient and the
redd steepness
Redd steepness of both artificial redds housing the incubation baskets and redds built
by sockeye in the two reaches were measured (Fig. 3.9). The redd steepness along the
profile of the redd was measured and calculated as the rise or the difference in water
depth between the deepest point of the trough and the highest point of the hummock
(h1-h2) divided by the run or distance (d) between these same points in the trough and
hummock.
Redd Profile
Flow
Figure 3.9. Redd profile labelling dimension measurements
Hydraulic gradient
Redd gradient
Hummock Depth
Trough Depth
Distance
62
For each redd investigated, water depth in the deepest part of the trough and
shallowest of the hummock was measured. The difference between the depth of the
trough and hummock was then divided by the distance between the two to calculate the
steepness of the redd. Superimposed redds were noted and avoided20.
Redds were measured during spawning (October) when fish could be observed holding
over redds. Once spawning activity (e.g. digging) had ceased, the redd was assumed to
be complete. Over the two years of this study, 2002 and 2003, 18 and 19 redds were
measured in the natural and channelized reaches respectively. There were fewer redds
in the channelized reach in 2002 due to low numbers of returning sockeye that year,
most of which spawned in the natural reach. The 37 measurements of redds built by
sockeye were compared with the 21 artificial redds placed in both reaches where egg
incubation survival rates and fine sediment accumulation were measured.
To test for differences between the gradients of redds built by sockeye in the natural
and channelized reaches, a two-tailed, two sample, non-parametric, Mann-Whitney U
test statistic was used. This test was selected due to the data not being normally
distributed. This same test was used to compare the redd steepness of the artificial
redds in the natural and channelized reaches. To test for differences between the
gradients of artificial redds and those built be salmon, a two-tailed, two-sample, t-test
was selected because the frequency of values for both artificial and sockeye built redds
together were normally distributed.
20 Superimposed redds are those built on top of former redd sites.
63
3.3 RESULTS
3.3.1. Egg survival
In 2003, egg incubation survivals were highest in the natural reach (54.1 ± 42.6%) and
lowest in the channelized reach (31.0 ± 24.2%; Table 3.1 Appendix 3D). These results
are within the expected range for wild Pacific Northwest sockeye populations21. No
significant difference was detected between the two reaches using a Student t-test
(p=0.31). The power of this test is very low (power < 0.35), suggesting there is an >
65% chance of making a Type II error22. Small sample size and high variability among
survivals precluded a statistically rigorous evaluation of survival by reaches. The small
sample size is due to the loss of approximately a third of the samples that suffered 0%
fertilization success in 2003.
Table 3.1. Mean and range of egg survivals in the three reaches in 2003
Habitat type Mean (S%)
Standard Deviation
Sample size
Natural 54.1 ± 42.6 6
Channelized 31.0 ± 24.2 5
There was high variability of survival (0-100%) among the reaches and even between
sites within reaches (Fig. 3.10). The channelized reach sites 1 and 2 had survivals that
ranged closely 30.7 ±14.5% and 31.2 ± 32.6% respectively. The two natural reach sites,
sites 3 and 4, contained high variation with egg survivals ranging 18.6 ± 12.5% and
89.6 ± 24.6% respectively. The low egg survivals found in site 3 were unexpected given
that in 2002 egg survivals in sites 3 and 4 ranged similarly with hatch and emergence
survival of 5.3 ± 7.1% and 4.0 ± 3.9% respectively. The egg survivals in site 3 may be 21 Hyatt, K. Head, Salmon in Regional Ecosystems Program, Science Branch Fisheries and Oceans
Canada, Pacific Biological Station, Nanaimo, BC. Personal communication, Email March 11, 2004. 22 Type II error is the error made if the (null) hypothesis is false but not rejected.
64
low because of poorer egg fertilization on that day (Oct. 17th) or due to the gradient of
the artificial redd which will be explained in more detail in the following sections.
Egg incubation survival by habitat types
0
20
40
60
80
100
120
natural channel
Habitat types
Su
rviv
al
(%)
Figure 3.10. Average pre-hatch egg incubation survivals by reaches in 2003
The sizes of gravel in the hummocks of redds built by sockeye was compared with the
sizes of gravel placed in incubation baskets to verify that the substrate composition in
the artificial redds was representative of redds built by sockeye. Substrate sizes in the
incubation baskets in the channelized and natural reaches average 28 ± 3mm and 32 ±
4mm respectively; the average substrate in hummocks of redds built by sockeye was
30 ± 6mm in both reaches. This difference is not significant (p=0.73); therefore, the
gravel placed in incubation baskets in artificial redds is representative of gravel found in
the hummock of naturally created redds.
Site 4
Site 3 Site 1
Site 2
65
3.3.2 Inter-gravel Dissolved Oxygen (IDO)
Inter-gravel dissolved oxygen values ranged from 9.1 to 13.1 mg/l (Fig. 3.11; Appendix
3E) which are within the IDO requirements for incubating eggs (Cope 1996; Peterson
and Quinn 1996). The mean IDO in the natural and channelized reaches are 11.6 ± 1.4
and 9.9 ± 1.8 mg/L respectively. Of the three sampling sessions the IDO values dipped
lowest in January when the eggs are just about to hatch (Long 2002; Lawrence 2003).
This time is known to be the most sensitive with the highest demand for IDO (Davis
1975; Peterson and Quinn 1996). Using a conservative estimate of 4 mg/l as the lower
lethal limit23, the IDO readings in all cases were within the range tolerated by salmon
eggs with the lowest reading of 4.6 mg/l measured. This was measured in the
channelized reach in January. The IDO levels were highly variable and it is unclear if
the methods and equipment used were partially responsible, but the average
channelized reach value was lower.
23 Cope (1996) found that optimum IDO for incubating salmon eggs is >5mg/l where Davis (1975) specified
optimum IDO between 6.5 and 9.75 mg/l. The threshold of IDO below which survival decrease rapidly (lower lethal limit) has been documented as 3.98mg/l (Davis 1975), 2mg/l (Koski 1975) and as low as 1.67 mg/l (Wickett 1954; Silver et al. 1963).
66
Intragravel dissolved oxygen in the Natural reach 2002/2003
0
5
10
15
20
25
30
0-1.9 2-3.9 4-5.9 6-7.9 8-9.9 10-11.9 12-13.9 14-16
Dissolved oxygen (mg/L)
Fre
qu
en
cy
OctoberJanuraryFebruary
Intragravel Dissolved oxygen in the Channel reach 2002/2003
0
2
4
6
8
10
12
14
16
0-1.9 2-3.9 4-5.9 6-7.9 8-9.9 10-11.9 12-13.9 14-16
Dissolved oxygen (mg/L)
Fre
qu
en
cy
OctoberJanuaryFebruary
Figure 3.11. Inter-gravel Dissolved oxygen measurements
Lower lethal limit
Compromised Develop
Mean 9.9 ± 1.8
(sample size =65)
Mean 11.6 ± 1.4 (sample size =68)
Compromised Develop
Lower lethal limit
67
3.3.3. Redd substrate measurements
Gravel substrate sizes in the channelized and natural reaches averaged 28 ± 3mm and
32 ± 4mm respectively, which is not significantly different between the reaches
(p=0.73). The hydraulic conductivity, therefore, will be driven by the amount of fines
measured in the artificial redds.
Fines accumulated within incubation baskets were analyzed by weight and by volume in
2003. By volume, accumulated fines (f%) are expressed as percent of fines (< 2 mm) in
terms of the available space (volume) within the basket (Figure 3.12, Appendix 3F). In
general, higher fines were found in the channelized reach (5.87 ± 4.3%) than in the
natural reach (2.10 ± 1.4%), and there was a significant difference between percent
fines. The proportion of fine sediment (< 2 mm) is higher in the channelized than the
natural reach.
Fine Sediment accumulation in Incubation baskets
0.00
2.00
4.00
6.00
8.00
10.00
12.00
Channel Natural
Fine
sed
imen
t acc
umul
atio
n (%
)
Figure 3.12. Ranges of accumulated fine sediment by reach in 2003
68
A literature review found that fines that are <0.833 mm in diameter negatively affect
salmon embryos (McNeill and Ahnell 1964; Waters 1995). Because the incubation
baskets accumulate fines <2 mm due to the size of the baskets mesh, accumulated fine
sediment was also analyzed by weight of each of six size fractions (sieve sizes: 1 mm,
0.5 mm, 0.25 mm, 0.15 mm, 0.037 mm, < 0.037 mm). Unfortunately sieve sizes do not
define sediments <0.833 mm and for this reason fines are described as either <1 mm or
>1 mm. Since the analysis of fines by volume is according to fines <2 mm, the ratio of
sand (>1 mm) to fines (<1 mm) is considered in order to verify that the volume of sand
particles – which is not known to negatively impact incubating eggs and is similar in the
two reaches – did not skew results on the volume of fines. The ratio of sand (>1 mm) to
fines (<1 mm) is also similar in artificial redds in the two reaches (Fig. 3.13).
Ratio of sand to fine sediment
0.00
0.10
0.20
0.30
0.40
0.50
0.60
0.70
0.80
0.90
Channelized NaturalPer
cent
of s
edim
ent a
ccum
ulat
ed w
ithin
the
incu
batio
n ba
sket
s by
wei
ght (
g)
Fine (≤1mm)Sand (>1mm)
Figure 3.13. Ratio of sand (> 1 mm) to fines (< 1 mm) in artificial redds (by weight in
grams)
69
3.3.4. Redd steepness measurements
The mean average steepness of redds built by sockeye in the natural reach were found
to be significantly lower than those of the channelized reach (p= 0.008). The mean
gradient of redds built by sockeye in the channelized reach was 16.5% compared with
an average gradient of 12.3% for redds in the natural reach (Table 3.2; Appendix 3G).
Table 3.2. The mean redd steepness of artificial redds and redds built by sockeye
Redd steepness Natural Reach
Channelized reach
Both Reaches
Sockeye built redds 12.3 ± 3.7% 16.5 ± 5.0% 15.6 ± 6.4%
Artificial redds 24.7 ± 9.5% 26.3 ± 7.7% 25.5 ± 8.4%
By comparison, the artificial redd steepness was not significantly different between the
two reaches (p=0.83) but the artificial redds were much steeper (25.5% on average)
than sockeye-built redds. The artificial redds were made in the same fashion in both
reaches except for artificial redds in site 3 of the natural reach which were built with the
gradients of 11% and 13%, the lowest among artificial redds.
3.4 DISCUSSION
I predicted that egg survival and IDO levels were not significantly different in redds
selected in either the natural or channelized reaches since the redd sites selected by
sockeye salmon were based on similar Froude numbers (Fr=0.315 ± 0.10). Although
this was the overall case (p=0.31), the power of this test was low, which is partially
attributed to a high amount of variation in egg incubation survivals between reaches
and sites. The resulting variation was highest in the natural reach with egg incubation
survivals of 54.1 ± 42.6% and lowest in the channelized reach (31.0 ± 24.2%).
70
Differences also occurred between the two sites within the natural reach as egg
survivals in site 3 (18.6 ± 12.5%) were much lower than site 4 (89.6 ± 24.6%). The high
variability among egg survivals in incubation baskets (ranging from 0 to 100%) has also
been found in other studies (Bardonnet and Bagliniére 2000; Cunjak et al. 2002).
Bardonnet and Bagliniére (2000) suggested that the high variability in egg survivals
could be associated with significant changes in IDO due to different paths of inter-gravel
flow within each basket or redd which is also known to occur temporally within egg
pockets (Peterson and Quinn 1996). A number of estimates exist specifying the
threshold of IDO below which egg survival decrease rapidly (lower lethal limit). These
estimates include, IDO values of 3.98mg/l (Davis 1975), 2mg/l (Koski 1975) and as low
as 1.67 mg/l (Wickett 1954; Silver et al. 1963). Even using a conservative estimate of 4
mg/l as the lower lethal limit, the IDO readings (ranging 9.1 to 13.1 mg/l) were within the
range required by salmon eggs (Cope 1996; Peterson and Quinn 1996). Development,
however, may be compromised when eggs experience IDO <6.0 mg/l, which have the
most critical effects during pre-hatch or early incubation (Davis 1975; Peterson and
Quinn 1996). For Okanagan sockeye, this occurs between December and February
(Long 2002; Lawrence 2003). IDO recorded in the channelized reach in January were
as low as 4.6 mg/l, well below the level (6.0mg/l) known where egg development
becomes compromised.
Although several factors affect IDO (Bjornn and Reiser 1991), the primary source of
high oxygen concentrations in water is the stream and the interchange of flowing water
through streambed gravels (Sheridan 1962 in Lacroix 1980). This movement of water is
associated with the amount and size of inter-gravel pore spaces, or hydraulic
71
conductivity, as it moves through the redd, whose angle on the streambed can be
measured as the hydraulic gradient. This ratio of hydraulic conductivity to hydraulic
gradient, measured as Darcy’s Law, controls the quantity of water flowing past
individual eggs (Zimmerman and Lapointe 2005).
The hydraulic conductivity would be lower in the channelized reach due to a
significantly greater proportion of fines (5.87 ± 4.3%) than in the natural reach (2.10 ±
1.4%) where similar gravel matrices were measured. Although compromised egg
survival has been associated with the presence of high percent fines (Harrison 1923 in
Chapman 1988; McNeil and Ahnell 1964), the amount of fines in the reaches studied
were less than those known to decrease survival. Hall and Lantz (1969) documented
that the percent of embryo survival had little affect with fines <15% and McNeill and
Ahnell (1964) noted decreases in egg survival when fines were >10%. Only one basket
had fines that exceeded 10% (site 2 in the channelized reach) and none exceeded 15%
fines. Fines <11% were found in another study24 freeze core sampling Okanagan
sockeye redds in 2002 (Rebellato et al. 2002).
Fines likely are low in the study reaches because of the close proximity below Vaseux
Lake where sediments have settled out. Higher amounts of fines in the channelized
reach exist because the river slope is very low (0.06%) (Bull et al. 2000) compared to
10% slopes found in the natural reach. Consequently, there is less flushing of sediment
at higher flows in the channelized reach. Even with the fishes’ efforts to increase gravel
permeability by removing fines - one of the important functions of building redds - the
24 To determine the depths within the hummock that sockeye eggs are found, freeze core sampling was
used. The depth of Okanagan sockeye eggs in redds was identified in order to refine the redd scour potential for the development of a model used by Okanagan River water managers.
72
amount of fines found in the river affects the amounts accumulated in redds during the
incubation period.
The techniques used by salmon to build a redd are similar not only among individuals
but also among species and between rivers (Burner 1951; Chapman 1988; Fabricus
and Gustafson 1954; Hobbs 1937; Jones 1959; Kondolf et al. 1993; Mathisen 1955 in
Forester 1968; McCart 1969; Needham 1961; White 1942; Young, et al. 1989).
However, differences in the gradient of the redd, were found in the two reaches studied
(Fig. 3.14). The gradient of redds built by sockeye in the channelized reach (16.5 ±
5.0%) were found to be significantly higher than that of the natural reach (12.3 ± 3.7%).
The trends in gradients seen in redds built by sockeye were not duplicated in the
artificial redds where egg survival rates were measured. The gradients of artificial redds
were found to be much higher and similar between the natural and channelized reaches
with values of 24.7 ± 9.5% and 26.3 ± 7.7% respectively. Consequently the gradients of
artificial redds are not representative of redds built by sockeye.
Redd profiles of artificial and sockeye built redds in the natural and channel reaches
-20
-15
-10
-5
0
5
10
15
-100.0 -50.0 0.0 50.0 100.0 150.0
Redd length (cm)
Red
d de
pth
prof
ile (c
m)
SK built channel redds
SK built natural redds
Artif icial channel redds
Artif icial natural redds
Figure 3.14. Profiles of redds artificial and built by sockeye in the two reaches
73
Using Darcy’s Law, I predicted that combinations of high values of accumulated fine
sediment and/or low redd steepness will produce reduced amounts of flow through the
redd. This can explain some of the lower egg survival rates. Lower egg survivals in
artificial redds in the channelized reach are due to the potentially less inter-gravel flow
supplied because this reach contains more fine sediment yet redd steepness similar to
the natural reach (similar artificial redd steepness). In the case of lower egg survivals in
artificial redds in site 3 within the natural reach, there is potentially less inter-gravel flow
supplied at these redds because although artificial redds in sites 3 and 4 have a similar
amounts of fine sediment- the redd steepness is lower (11% and 13%) in site 3
compared to the site 4 (19% and 20%).
Redds built by sockeye, however, do not mimic the gradients found in artificial redds.
Redd steepness was found to be significantly higher in the channelized reach than in
the natural reach. In the channelized reach the higher fine sediment accumulations and
the higher redd steepness produces a potentially similar flow through the redd as when
compared to the fewer fines and lower redd steepness of the natural reach. Similar flow
through the redd between the two reaches might mean similar egg survivals between
the two reaches; however, since the flow through the gravel was not measured it is
unclear if this is be the case because the steeper redds in the channelized reach still
may not be enough to compensate for the higher amounts of fines and therefore egg
survivals would be compromised in this reach. It is also unclear what the impact of
building a steeper redd would have on the adults. A steeper redd may have a high cost
to the fish as they are harder to build and some may not always be able in which case
the egg survival in the redd may suffer.
74
The reason Okanagan sockeye create steeper redds in gravels with greater fine
accumulations may be because the steeper redds produce an inter-gravel flow that
creates an up-welling of water. This up-welling may be noticed by the fish because, in
areas of greater up-welling, the force of upward flow opposes the force of gravity which
increases the buoyancy of the substrate. Through the process of ‘digging’ the redd and
creating a suction force, or shear stress, by the undulating tail movements against the
substrate, the fish are also trying to make the substrate more mobile. When enough up-
welling occurs, the bed substrate is easier to move. This up-welling is potentially
created by the fish in the form of steeper gradient between the trough and the
hummock. Cooper (1965) documented that flows over flat gravel beds penetrate the
upper 15cm which equates to poor survival of eggs deeper than 15cm; however by
forming hummocks similar to those made by spawning salmon, inter-gravel circulation
penetrated to depths of 46cm (Fig. 3.3).
By building the redd (e.g. creating a steep gradient between the hummock and trough),
the newly created up-welling makes it easier for the fish to construct the redd and there
may also be a point of bed movement that signals to the fish that redd construction in
this substrate [or at this location] is the best for egg incubation survival. The ease of
moving gravel on a stream bed is related to the shear stress required because gravel
located on a steeper gradient (i.e. the hummock) experiences high amounts of shear
stress so it can be easily moved. In areas of low conductivity it takes a steeper gradient
in the redd to get the gravel moving to cover the eggs. If it is on a low gradient flat bed it
requires a greater difference in redd depth before the gravel can be moved to either dig
out the trough or cover the eggs. This can be experienced by standing in the river on a
gravel bar near the top of a riffle and observe how easily your boots can shift the gravel
around. The higher water surface gradient actually creates enough shear stress to
75
undermine your feet illustrating how little effort would be required by the fish to build a
redd. On the other hand, in a low gradient reach, one would need to kick the substrate
with a great deal of force to get it to move.
Evidence that salmon are selective not only of the redd site but also during the redd
building process exists in the ‘testing25’ of redds during construction (Mathisen 1955;
Needham 1961; Jones 1959). Testing redds suggests that even once redd sites are
selected the fish are modifying the redd to produce a size or perhaps redd steepness
that creates a degree of up-welling that facilitates the redd’s construction and
subsequently egg survival.
Using Darcy’s Law as a model of inter-gravel flow impacts on egg survival has
uncovered two significant implications. First, an increase in fines in the channelized
reach translates into the need for fish to build a higher gradient redd to create similar
interstitial flows. This is noticed by the fish through the ease of building the redd at
these steeper gradients, however the building of a steeper redd may have an energy
cost to the fish. The second implication for survival between the natural and
channelized reaches is that methods such as the incubation baskets to measure egg
survival in artificial redds will need to take into account the steepness of the artificial
redd built as this seems to effect the success of the incubating eggs. To conclude, this
study has identified Darcy’s Law as a potential application for explaining some variables
of egg survival. By taking these findings into account for future research, a better
understanding of the factors affecting egg survival will ensue.
25 Female salmon have been documented ‘testing’ redds by using their anal fin moving slowly over and
pushing against the gravel in the trough (Needham 1961).
76
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alevins of Atlantic salmon and brook trout in relation to fine sediment deposition.
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85
4.0 CONCLUSION
Okanagan sockeye select sites and build redds where flow types can be predicted by
the Froude number (0.315 ± 0.10). Although the range of Froude numbers differed
significantly from the average Froude number used by Atlantic salmon in Scotland (Fr =
0.344; Moir et al. 1999), it was within the range also found in this study. Although more
work needs to be done, the use of the Froude number to describe spawning areas
selected can be accepted as applicable to other salmon species and other rivers.
Between the two hydraulically different study reaches, the natural reach contained the
range of selected Froude numbers in low and average water discharge years sampled.
The channelized reach produced selected Froude numbers mostly when discharge was
lower than average. Because of the homogeneous nature of the channelized reach, the
range of available Froude numbers represents the total range found within the reach,
however the range in the natural reach measured at the two sites is most likely only a
portion of the total range due to the heterogeneity of the natural reach. Restoring a
section of the channelized reach to replicate the natural reach’s heterogeneous
environment will increase the likelihood of preferred spawning areas at a greater range
of discharge levels.
At selected spawning sites (Fr = 0.315 ± 0.10) in both reaches, egg survival in artificial
redds was measured. Egg survival was found to be statistically similar but highly
variable between not only the two reaches studied but also between sites within the
natural reach. Generally, lower egg survival was recorded in the channelized reach by
comparison to the natural reach and within the natural reach there was lower survivals
at sites 3 compared to high amounts of egg survival documented at site 4.
86
Using substrate composition and redd steepness the potential flow through the redd
was used to explain the variations in egg survival. Redds with estimates of either low
fine accumulations (i.e. the natural reach) or steeper redds (i.e. artificial redds) were
found to support higher amounts of egg survival. In the channelized reach where higher
fines accumulate, steeper redds were also measured. These conditions may mean that
the flow through redds are similar in redds built by sockeye in the two reaches when
they are built however, since the flow through the gravel was not measured it is unclear
if this would be the case because steeper redds in the channelized reach may still not
be enough to compensate for the higher amounts of fines; therefore, egg survivals
would be compromised in this reach. It is also unclear what the impacts of building a
steeper redd in the channelized reach would have on the adults, whose energy
reserves at this point in their lifecycle are diminishing, and the quality of the resulting
redds.
Evidence to support this theory can be found in the artificial redds in site 3 and 4. At
both sites, the accumulation of fines was similar but egg survival differed. This may be
attributed to the lower redd steepness in artificial redds in site 3 built at the end of they
day by a crew who did not have the energy reserves to build the steeper artificial redds
typically made. To conclude, this research points out benefits and implications for
creating more heterogeneous (i.e. natural) channel reconstruction. Moving away from a
homogeneous environment will increase likelihood of preferred spawning and
incubation flows therefore improving egg (and species) survival. Future studies
measuring egg survivals in artificial redds need to account for the steepness of the redd
that is built in relation to the system being studied, and this includes taking into account
the Froude values of the flows.
87
APPENDIX 2-A: Summary of salmon spawning site selection research
Site selection factors Study description
Water depth and velocity
explanation of spawning site selection is species specific with preferences for depth and velocity (Montgomery et al. 1999; Burner 1951; Smith 1973)
with suitable spawning gravel rainbow trout spawn in areas of high water velocities and depths, where such areas were not suitable at different discharges (Hartman and Galbraith 1970 in Lacroix 1980)
Atlantic salmon select water depths above a specific minimum and focal water velocities within a range, irrespective of the stream discharge rates (Lacroix 1980)
fish use consistent depths and velocities during all flow conditions (Grost et al. 1990 in Thurlow and King 1994)
redds occurred in high velocity areas characterized by a sharp velocity gradient (Lacroix 1980)
the microhabitat of spawning golden trout redds were shallower while average velocities at redds were significantly faster over what was a wide range (Knapp and Vredenburg 1996)
there is a dependence between the river beds, the steepness of the velocity gradient and the intensity of shear stress on the bed therefore salmon could select either specific substrate or velocity (Leopold et al 1964 in Lacroix 1980)
water depths and velocities at redd locations were similar despite differences in available habitat (Parsons and Hubert 1988)
brown trout chose positions with optimum combinations of depth and velocity with more preferred valued than of either factor alone (Shirvell and Dungey 1983)
Fish select velocities as an indicator of substrate (Shrivell and Dungey 1983)
kokanee select certain water depths, velocities and substrate sizes but these three variables were not sufficient to fully account for spawning site selection (Muller and Hubert 1995)
up to 85% of the variation in depth in the redd was explained by depth at a location outside the redd (Thurlow and King 1994)
Hydraulic variables
at the local scale, the nature of hydraulic (flow depth, velocity and Froude no) and sedimentary controls in spawning habitat are important (Kondolf and Wolman 1993)
fish select sites of riffle crests or pool tails otherwise known as transitional areas between pools and riffles (Barnard 1992; Hunter 1991; White 1942; Stuart 1953; Stuart 1954; Hazzard 1932; Hobbs 1937; Smith 1941; Briggs 1953)
fish may select a particular combination of depth and velocity values which is best described by the Froude number (Moir et al. 1998)
88
APPENDIX 2-A: cont. Site selection
factors Study description
Stream discharge
cutthroat trout choose new spawning locations in years of different flows (Thurlow and King 1994)
discharge and chum spawner recruitment were positively correlated inferring that discharge flow is a dominant factor in attracting spawners to a channel (Cowan 1991)
no evidence that changes in daily flow affected chinook redd distribution downstream of Priest Rapids Dam on the Columbia River or that daily flow fluctuations prevent female from completing the redd (Chapman et al. 1986)
redd site selection may be controlled by patterns of bed mobility and discharge predictability (Montgomery et al. 1999)
the area of spawning varies according to discharge rates and channel gradients (Benda et al. 1992)
Slope at the reach scale, bed slope exerts a strong influence of spawning distribution by controlling the distribution of spawning sediments (Moir et al. 1998; Mills 1973; Crisp 1996 in Moir et al 1998; Benda et al. 1992)
Substrate Salmon select hydraulic conditions such that fine sediments are sorted out (Platts et al. 1979 in Barnard 1992)
salmon have preferences for certain substances at spawning sites (Hasler and Scholz 1983; Burner 1951; Hoopes 1972; Tautz and Groot 1975; Reiser and Bjornn 1979; Lacroix 1980)
kokanee also seemed to select spawning sites with recently deposited substrate particles (Muller and Hubert 1995).
Since utilization of habitat components is influenced by availability the gravel sizes used may vary with the sizes available (Baldrige and Amos 1981 in Kondolf and Wolman 1993)
concluded that selection of spawning sites is determined by visual stimuli of particle sizes seen by the female (Needham 1961)
Bed stability from redd count data over (1966-1996), more heavily utilized sites may reflect areas where bed sediment have remained relatively stable (Moir et al. 1998)
seasonal flow stability was an important factor determining the suitability of spawning sites (Hartman and Galbraith 1970; in Lacroix 1980)
Biological factors
found that fish were attracted to site specific odors (Blair and Quinn 1991)
Other biological variables such as predation and intra-specific competition may have a significant sometimes dominant effect on spawning site location (Shirvel and Dungey 1983; Gibson 1993 in Moir et al 1998)
competition among salmon can force the fish into less preferred areas (Shrivell and Dungey 1983)
89
APPENDIX 2-A: cont. Site selection
factors Study description
Groundwater and permeability
sockeye select redd sites in places with the strongest current of ground water. Experiments show that sockeye placed in penned off areas where there is not flow of groundwater, do not deposit their eggs (Krogius and Krokhin 1956; in Foerster 1968)
salmon select areas of down-welling indirectly by selecting factors conducive to flow characteristics such as slope on upstream edge which increases permeability in the direction of flow and the acceleration of water current (Lacroix 1980)
in streams with gravel covered clay where fish start then abandon redds making it unlikely that initiation requires up or down-welling flow but that at certain stages of cutting redds require the presence of suitable intra-gravel flow (Crisp and Carling 1989)
field observations suggest there is a regular downward flow of water through the gravel beneath the river bed at the sites favoured by spawning salmon and trout (Stuart 1954; Witzel and MacCrimmon 1983; Sowden and Power. 1985)
percolation of water through the gravel appears to be a prerequisite of the redd sites (Burner 1951)
Accelerated flow and upwelling rather than just velocity may determine choice of spawning locations (Tautz and Groot 1975 in Thurlow and King 1994; Webster and Eiriksdottir 1976)
Dissolved oxygen
found that intra-gravel dissolved oxygen was the limiting factor in sockeye choosing spawning sites (Wood 1995)
Other factors streambed topography, gravel size and compaction, velocity gradients and profiles and current patterns are possible important cues in the selection of suitable areas (Lacroix 1980)
No preference
No preference for the expected sites has been reported by some authors (Hansen 1975; Ottoway et al. 1981)
90
APPENDIX 2-B: Measurement taken above redd sites selected
Reach Water depth (m)
Average velocity (m/s)
Froude number
Reynolds number Reach
Water depth (m)
Average velocity (m/s)
Froude number
Reynolds number
channel 0.57 0.57 0.24 249,923 natural 0.23 0.56 0.37 99,077 channel 0.51 0.62 0.28 243,231 natural 0.18 0.50 0.38 69,231 channel 0.41 0.50 0.25 157,692 natural 0.21 0.61 0.42 98,538 channel 0.39 0.42 0.21 126,000 natural 0.23 0.39 0.26 69,000 channel 0.31 0.31 0.18 73,923 natural 0.26 0.38 0.24 76,000 channel 0.39 0.49 0.25 147,000 natural 0.25 0.58 0.37 111,538 channel 0.43 0.63 0.31 208,385 natural 0.2 0.68 0.49 104,615 channel 0.57 0.50 0.21 219,231 natural 0.3 0.61 0.36 140,769 channel 0.29 0.31 0.18 69,154 natural 0.26 0.95 0.59 190,000 channel 0.51 0.45 0.20 176,538 natural 0.32 0.31 0.17 76,308 channel 0.55 0.63 0.27 266,538 natural 0.25 0.35 0.22 67,308 channel 0.39 0.50 0.26 150,000 natural 0.21 0.36 0.25 58,154 channel 0.43 0.42 0.20 138,923 natural 0.22 0.45 0.31 76,154 channel 0.32 0.44 0.25 108,308 natural 0.18 0.54 0.41 74,769 channel 0.63 0.51 0.21 247,154 natural 0.42 0.32 0.16 103,385 channel 0.3 0.57 0.33 131,538 natural 0.28 0.54 0.33 116,308 channel 0.38 0.79 0.41 230,923 natural 0.45 0.55 0.26 190,385 channel 0.27 0.59 0.36 122,538 natural 0.24 0.56 0.36 103,385 channel 0.38 0.81 0.42 236,769 natural 0.19 0.46 0.34 67,231 channel 0.47 0.62 0.29 224,154 natural 0.14 0.35 0.30 37,692 channel 0.29 0.41 0.24 91,462 natural 0.2 0.68 0.49 104,615 channel 0.4 0.36 0.18 110,769 natural 0.2 0.60 0.43 92,308 channel 0.55 0.88 0.38 372,308 natural 0.34 0.23 0.13 60,154 channel 0.62 0.82 0.33 391,077 natural 0.22 0.29 0.20 49,077 channel 0.4 0.57 0.29 175,385 natural 0.15 0.34 0.28 39,231 channel 0.35 0.52 0.28 140,000 natural 0.28 0.50 0.30 107,692 channel 0.3 0.51 0.30 117,692 natural 0.5 0.64 0.29 246,154 channel 0.45 0.49 0.23 169,615 natural 0.22 0.50 0.34 84,615 channel 0.29 0.38 0.23 84,769 natural 0.27 0.45 0.28 93,462 channel 0.27 0.38 0.23 78,923 natural 0.43 0.39 0.19 129,000 channel 0.4 0.52 0.26 160,000 natural 0.67 0.17 0.07 87,615 channel 0.40 0.88 0.44 270,769 natural 0.52 0.38 0.17 152,000 channel 0.54 0.86 0.37 357,231 natural 0.39 0.40 0.20 120,000 channel 0.47 0.86 0.40 310,923 natural 0.35 0.38 0.21 102,308 channel 0.49 0.85 0.39 318,500 natural 0.39 0.56 0.29 168,000 channel 0.48 0.77 0.35 282,462 natural 0.37 0.45 0.24 128,077 channel 0.47 0.91 0.42 329,000 natural 0.3 0.38 0.22 87,692 channel 0.33 0.88 0.49 223,385 natural 0.28 0.46 0.28 99,077 channel 0.48 0.87 0.40 319,385 natural 0.27 0.44 0.27 91,385 channel 0.37 0.97 0.51 276,077 natural 0.25 0.49 0.31 94,231 channel 0.43 0.85 0.41 279,500 natural 0.22 0.23 0.16 38,923 channel 0.37 1.06 0.56 301,692 natural 0.27 0.42 0.26 87,923 channel 0.60 0.86 0.35 396,923 natural 0.26 0.28 0.18 56,000 channel 0.43 0.70 0.34 231,538 natural 0.23 0.59 0.39 104,385 channel 0.52 0.78 0.35 312,000 natural 0.26 0.43 0.27 86,000 channel 0.53 0.85 0.37 344,500 natural 0.24 0.54 0.35 99,077 channel 0.72 0.94 0.35 520,615 natural 0.30 0.48 0.28 110,769 channel 0.46 0.83 0.39 293,692 natural 0.20 0.19 0.13 28,462 channel 0.54 0.98 0.42 405,000 natural 0.22 0.62 0.42 104,923 channel 0.53 0.89 0.39 360,808 natural 0.20 0.43 0.31 65,769 channel 0.52 0.68 0.30 272,000 natural 0.26 0.29 0.18 57,000 channel 0.72 0.85 0.32 470,769 natural 0.16 0.32 0.26 39,385 channel 0.70 0.77 0.29 411,923 natural 0.18 0.23 0.17 31,500 channel 0.62 0.64 0.26 302,846 natural 0.20 0.28 0.20 43,462 channel 0.45 0.75 0.36 259,615 natural 0.20 0.22 0.16 34,231 channel 0.31 0.70 0.40 166,923 natural 0.23 0.63 0.42 108,606 channel 0.34 0.37 0.20 95,462 natural 0.20 0.45 0.32 69,615 channel 0.32 0.42 0.23 102,154 natural 0.24 0.43 0.28 78,462
91
APPENDIX 2-B: cont.
Reach Water depth (m)
Average velocity (m/s)
Froude number
Reynolds number Reach
Water depth (m)
Average velocity (m/s)
Froude number
Reynolds number
channel 0.23 0.22 0.15 38,923 natural 0.26 0.52 0.32 103,000 channel 0.19 0.35 0.26 51,154 natural 0.20 0.52 0.37 80,385 channel 0.32 0.36 0.20 88,615 natural 0.19 0.56 0.41 81,115 channel 0.33 0.55 0.30 138,346 natural 0.25 0.32 0.21 62,019 channel 0.49 0.83 0.38 312,846 natural 0.25 0.42 0.26 79,808 channel 0.41 1.06 0.53 332,731 natural 0.26 0.34 0.21 68,500 channel 0.40 1.08 0.55 332,308 natural 0.15 0.65 0.53 74,423 channel 0.43 0.69 0.33 226,577 natural 0.13 0.36 0.31 35,500 channel 0.37 0.67 0.35 189,269 natural 0.16 0.43 0.34 52,923 channel 0.47 0.81 0.38 292,846 natural 0.21 0.83 0.57 133,269 channel 0.35 0.86 0.46 231,538 natural 0.76 0.68 0.25 397,538 channel 0.44 0.86 0.41 289,385 natural 0.66 0.62 0.24 314,769 channel 0.42 0.78 0.38 250,385 natural 0.65 0.70 0.28 347,500 channel 0.46 1.08 0.51 382,154 natural 0.56 0.94 0.40 404,923 channel 0.46 1.04 0.49 366,231 natural 0.57 0.81 0.34 355,154 channel 0.60 0.69 0.28 316,154 natural 0.54 0.76 0.33 315,692 channel 0.74 0.66 0.24 372,846 natural 0.45 0.89 0.42 308,077 channel 0.67 0.68 0.27 350,462 natural 0.56 0.71 0.30 303,692 channel 0.67 0.50 0.19 255,115 natural 0.57 0.61 0.26 265,269 channel 0.68 0.58 0.22 303,385 natural 0.43 0.53 0.26 175,308 channel 0.64 0.72 0.29 352,000 natural 0.62 0.64 0.26 305,231 channel 0.31 0.43 0.25 102,538 natural 0.60 0.66 0.27 302,308 channel 0.30 0.49 0.29 113,077 natural 0.60 0.72 0.29 330,000 channel 0.48 0.68 0.31 251,077 natural 0.67 0.63 0.25 324,692 channel 0.39 0.81 0.41 241,500 natural 0.68 0.64 0.25 332,154 channel 0.52 0.75 0.33 300,000 natural 0.58 0.70 0.29 310,077 channel 0.40 0.71 0.36 218,462 natural 0.64 0.62 0.25 305,231 channel 0.52 0.78 0.35 312,000 natural 0.56 0.62 0.26 264,923 channel 0.43 0.81 0.39 267,923 natural 0.33 0.48 0.27 121,846 channel 0.48 0.87 0.40 319,385 natural 0.25 0.46 0.29 88,462 channel 0.56 0.87 0.37 372,615 natural 0.42 0.38 0.18 121,154 channel 0.52 0.90 0.40 358,000 natural 0.58 0.46 0.19 203,000 channel 0.45 0.77 0.36 264,808 natural 0.65 0.57 0.22 282,500 channel 0.47 0.44 0.20 157,269 natural 0.61 0.68 0.28 316,731 channel 0.38 0.66 0.34 192,923 natural 0.60 0.63 0.26 288,462 channel 0.49 0.60 0.27 226,154 natural 0.53 0.54 0.24 220,154
natural 0.50 0.42 0.19 161,538 natural 0.42 0.82 0.40 263,308 natural 0.41 0.72 0.36 225,500 natural 0.63 0.70 0.28 339,231 natural 0.61 0.54 0.22 253,385 natural 0.70 0.86 0.33 463,077 natural 0.73 0.68 0.25 381,846 natural 0.62 0.68 0.28 324,308 natural 0.37 0.69 0.36 196,385 natural 0.27 0.81 0.50 168,231 natural 0.35 0.70 0.38 188,462 natural 0.38 0.33 0.17 95,000 natural 0.18 0.34 0.25 46,385 natural 0.17 0.70 0.54 91,538 natural 0.21 0.75 0.52 120,346 natural 0.26 0.79 0.49 157,000 natural 0.30 0.83 0.48 190,385 natural 0.35 0.82 0.44 219,423 natural 0.45 0.71 0.34 244,038 natural 0.20 0.77 0.55 118,462 natural 0.21 0.67 0.47 108,231 natural 0.19 0.67 0.49 97,192 natural 0.22 0.49 0.33 82,923 natural 0.17 0.58 0.45 75,192 natural 0.22 0.77 0.52 130,308 natural 0.37 0.36 0.19 101,038
92
APPENDIX 2-C: Physical features of the river available to spawning sockeye
Data Year Reach Grid Site No.
Depth (cm)
Average Velocity
(m/s)
Froude No.
Reynolds No.
2002 channel 2 58 0.49 0.21 218,615 2002 channel 2 42 0.42 0.21 135,692 2002 channel 2 50 0.49 0.22 188,462 2002 channel 2 58 0.53 0.22 236,462 2002 channel 2 62 0.55 0.22 262,308 2002 channel 2 60 0.55 0.23 253,846 2002 channel 2 54 0.53 0.23 220,154 2002 channel 2 51 0.52 0.23 204,000 2002 channel 2 54 0.56 0.24 232,615 2002 channel 2 58 0.60 0.25 267,692 2002 channel 2 60 0.62 0.26 286,154 2002 channel 2 42 0.53 0.26 171,231 2002 channel 2 60 0.64 0.26 295,385 2002 channel 2 66 0.68 0.27 345,231 2002 channel 2 58 0.65 0.27 290,000 2002 channel 2 62 0.68 0.28 324,308 2002 channel 2 56 0.67 0.29 288,615 2002 channel 2 58 0.73 0.31 325,692 2002 channel 2 50 0.68 0.31 261,538 2003 channel 1 19 0.12 0.09 17,538 2003 channel 1 27 0.15 0.09 31,154 2003 channel 1 23 0.14 0.09 24,769 2003 channel 1 28 0.18 0.11 38,769 2003 channel 1 27 0.19 0.12 39,462 2003 channel 1 71 0.32 0.12 174,769 2003 channel 1 18 0.17 0.13 23,538 2003 channel 1 38 0.29 0.15 84,769 2003 channel 1 49 0.33 0.15 124,385 2003 channel 1 30 0.26 0.15 60,000 2003 channel 1 70 0.44 0.17 236,923 2003 channel 1 86 0.52 0.18 344,000 2003 channel 1 64 0.45 0.18 221,538 2003 channel 1 43 0.37 0.18 122,385 2003 channel 1 69 0.47 0.18 249,462 2003 channel 2 52 0.42 0.19 168,000 2003 channel 1 47 0.43 0.20 155,462 2003 channel 1 31 0.35 0.20 83,462 2003 channel 2 39 0.42 0.21 126,000 2003 channel 1 61 0.56 0.23 262,769 2003 channel 1 77 0.63 0.23 373,154 2003 channel 1 65 0.66 0.26 330,000 2003 channel 2 27 0.48 0.29 99,692 2003 channel 2 38 0.57 0.30 166,615 2003 channel 2 41 0.64 0.32 201,846 2003 channel 2 36 0.73 0.39 202,154 2003 channel 2 42 0.80 0.39 258,462 2003 channel 2 34 0.75 0.41 196,154 2003 channel 2 42 0.86 0.42 277,846 2003 channel 2 35 0.87 0.47 234,231 2003 channel 2 29 0.84 0.50 187,385 2002 natural 4 45 0.02 0.01 6,923 2002 natural 4 47 0.03 0.01 10,846 2002 natural 4 50 0.21 0.09 80,769 2002 natural 4 43 0.30 0.15 99,231 2002 natural 4 19 0.33 0.24 48,231 2002 natural 4 38 0.36 0.19 105,231 2002 natural 4 29 0.36 0.21 80,308 2002 natural 4 42 0.38 0.19 122,769
93
APPENDIX 2-C: cont.
Data Year Reach Grid Site No.
Depth (cm)
Average Velocity
(m/s)
Froude No.
Reynolds No.
2002 natural 4 54 0.40 0.17 166,154 2002 natural 4 66 0.42 0.17 213,231 2002 natural 4 48 0.42 0.19 155,077 2002 natural 4 47 0.42 0.20 151,846 2002 natural 4 19 0.42 0.31 61,385 2002 natural 4 30 0.43 0.25 99,231 2002 natural 4 60 0.44 0.18 203,077 2002 natural 4 59 0.45 0.19 204,231 2002 natural 4 39 0.46 0.24 138,000 2002 natural 4 48 0.48 0.22 177,231 2002 natural 4 40 0.48 0.24 147,692 2002 natural 4 37 0.49 0.26 139,462 2002 natural 4 47 0.50 0.23 180,769 2002 natural 4 63 0.52 0.21 252,000 2002 natural 4 38 0.53 0.27 154,923 2002 natural 4 36 0.54 0.29 149,538 2002 natural 4 42 0.57 0.28 184,154 2002 natural 4 32 0.58 0.33 142,769 2002 natural 4 42 0.63 0.31 203,538 2002 natural 4 37 0.64 0.34 182,154 2002 natural 4 48 0.65 0.30 240,000 2002 natural 4 37 0.65 0.34 185,000 2002 natural 4 35 0.65 0.35 175,000 2002 natural 4 70 0.73 0.28 393,077 2003 natural 4 33 0.16 0.09 40,615 2003 natural 3 30 0.17 0.10 39,231 2003 natural 3 24 0.18 0.12 33,231 2003 natural 3 28 0.20 0.12 43,077 2003 natural 3 33 0.23 0.13 58,385 2003 natural 4 12 0.23 0.21 21,231 2003 natural 4 34 0.24 0.13 62,769 2003 natural 3 28 0.24 0.14 51,692 2003 natural 4 19 0.25 0.18 36,538 2003 natural 4 39 0.26 0.13 78,000 2003 natural 3 13 0.27 0.24 27,000 2003 natural 3 19 0.28 0.21 40,923 2003 natural 3 43 0.29 0.14 95,923 2003 natural 4 40 0.31 0.16 95,385 2003 natural 4 46 0.33 0.16 116,769 2003 natural 3 32 0.33 0.19 81,231 2003 natural 3 24 0.33 0.22 60,923 2003 natural 3 25 0.35 0.22 67,308 2003 natural 4 22 0.35 0.24 59,231 2003 natural 4 39 0.38 0.19 114,000 2003 natural 4 35 0.38 0.21 102,308 2003 natural 4 44 0.39 0.19 132,000 2003 natural 4 35 0.39 0.21 105,000 2003 natural 4 49 0.40 0.18 150,769 2003 natural 4 42 0.40 0.20 129,231 2003 natural 4 33 0.40 0.22 101,538 2003 natural 4 42 0.42 0.21 135,692 2003 natural 4 45 0.44 0.21 152,308 2003 natural 4 35 0.45 0.24 121,154 2003 natural 4 32 0.47 0.27 115,692 2003 natural 4 30 0.49 0.29 113,077 2003 natural 4 32 0.50 0.28 123,077 2003 natural 4 10 0.61 0.62 46,923 2003 natural 3 12 0.98 0.90 90,462
94
APPENDIX 3-A: Fertilization success estimates Table of fertilization success estimates from incubation basket and hatchery controls in 2002 and 2003
Year Number of dead
eggs
Number of eggs basket
Fertilization success estimate
Pooled fish
numbers
Hatchery incubation survival26
Control survival
2002 25 100 75% 75% 2002 80 100 20% 20% 2003 100 100 0% 0% 2003 13 100 87% 35-37
38-40 84% 94%
88%
2003 4 100 96% 47-62 71.6% 83% Control survival is an average of the fertilization success estimate and the hatchery incubation survivals for the pooled fish. Control survivals can be related to individual baskets based on the date the basket was set.
26 Hatchery egg survival was counted just before hatch December 18, 2003 by Shuswap hatchery
95
APPENDIX 3-B: Pre-hatch incubation survival of sockeye eggs in 2002 Eggs Alevin Site
# Basket
# Date set Date recovered
Egg age upon
recovery
Fertilization success estimate live dead29 Total
eggs live dead emerge
Survival to hatch
%27
Survival to emergence
%28 Comments
1 2 11-Oct 3-Feb hatch 75% 0 10 10 0 0 0.0 - Temp. tidbit 5336 1 24 15-Oct 3-Feb hatch 20% 0 100 100 0 0 0.0 - 1 25 15-Oct 3-Feb hatch 20% 0 84 84 0 0 0.0 - 1 27 15-Oct 3-Feb hatch 20% 0 100 100 0 0 0.0 - 1 26 15-Oct 3-Feb hatch 20% 0 118 118 0 0 0.0 - 1 3 11-Oct 28-May emerge 75% 54 54 0 0 0 - 0.0 1 4 11-Oct 28-May emerge 75% 58 58 0 0 0 - 0.0 Temp. tidbit 3024 1 5 11-Oct 28-May emerge 75% 62 63 0 0 1 - 1.3 1 1 11-Oct 28-May emerge 75% 59 59 0 0 0 - 0.0 1 23 15-Oct 28-May emerge 20% 65 65 0 0 0 - 0.0 2 7 11-Oct 4-Feb hatch 75% 0 103 103 0 0 0.0 - Temp. tidbit 8587 2 6 11-Oct 4-Feb hatch 75% 0 81 81 0 0 0.0 - 2 9 11-Oct 4-Feb hatch 75% 0 65 65 0 0 0.0 - 2 28 15-Oct 4-Feb hatch 20% 0 88 88 0 0 0.0 - 2 32 15-Oct 4-Feb hatch 20% 0 82 82 0 0 0.0 - 2 8 11-Oct 27-May emerge 75% 76 76 0 0 0 - 0.0 Temp. tidbit 5331 2 30 15-Oct 27-May emerge 20% 25 25 0 0 0 - 0.0 2 10 11-Oct 27-May emerge 75% 50 50 0 0 0 - 0.0 2 31 15-Oct 27-May emerge 20% 78 78 0 0 0 - 0.0 2 29 15-Oct 27-May emerge 20% 61 61 0 0 0 - 0.0 3 11 11-Oct 5-Feb hatch 75% 0 57 73 16 0 21.3 - Temp. tidbit 5338 3 36 15-Oct 5-Feb hatch 20% 0 58 59 1 0 1.3 - 3 33 15-Oct 5-Feb hatch 20% 0 65 65 0 0 0.0 - 3 35 15-Oct 5-Feb hatch 20% 2 74 76 0 0 2.7 - 3 34 15-Oct 5-Feb hatch 20% 0 93 94 1 0 1.3 - 3 13 11-Oct 28-May emerge 75% 28 37 0 0 9 - 12.0 3 14 11-Oct 28-May emerge 75% 63 68 2 3 0 - 2.7 3 15 11-Oct 28-May emerge 75% 49 50 0 0 1 - 1.3 3 12 11-Oct 28-May emerge 75% 43 51 0 0 8 - 10.7 Temp. tidbit 5337 3 37 15-Oct 28-May emerge 20% 39 39 0 0 0 - 0.0 4 17 11-Oct 6-Feb hatch 75% 0 104 111 7 0 9.3 - Temp. tidbit 5339 4 40 15-Oct 6-Feb hatch 20% 0 93 94 1 0 1.3 - 4 21 11-Oct 6-Feb hatch 75% 0 109 114 5 0 6.7 - 4 19 11-Oct 6-Feb hatch 75% 0 101 106 2 3 2.7 - 4 39 15-Oct 6-Feb hatch 20% 0 74 74 0 0 0.0 - 4 18 11-Oct 27-May emerge 75% 62 62 0 0 0 - 0.0 4 16 11-Oct 27-May emerge 75% 54 55 0 0 1 - 1.3 Temp. tidbit 3002 4 42 15-Oct 27-May emerge 20% 59 60 0 0 1 - 5.0 4 38 15-Oct 27-May emerge 20% 73 75 0 0 2 - 10.0
27 survival S(%)=[n/(i-m)]*100 28 same as above 29 black eggs were observed in 2002 but not counted separately
96
APPENDIX 3-C: Invertebrates found within incubation baskets upon recovery 2003
Potential predators of salmon eggs 30 Not egg predators (mostly grazers or filter feeders) Site No. common
stonefly giant
stonefly Caddisfly
spp. Flat-worm
netspinner caddisfly
casemake cadisfly
mayfly Blood-worm
Unknown (small)
1 24 1 1 1 3 1 31 1 2 7 1 2 1 1 2 2 2 2 4 29 2 2 2 7 2 1 1 13 3 2 12 1 3 2 14 17 3 1 1 4 16 3 6 2 3 3 4 2 4 6 11 7 4 5 8 2 4 4 4 4 4 3 22 4 3 3 1 42 4 3 2 1 11
30 Dr. Douglas Craig, Professor Emeritus University of Alberta, Edmonton
(Personal communication. email March 1st 2004)
97
APPENDIX 3-D: Pre-hatch incubation survival of sockeye eggs in 2003
Eggs Site #
Basket#
Date set
Date Recovered
Egg age upon
recovery
Control survival estimate live
total dead
dead black Total eggs
Survival % to hatch 31
1 30 17-Oct 10-Nov 1 month 89% 18 60 17 43 78 20.5 1 36 17-Oct 9-Dec 2 month 89% 36 53 23 30 89 40.9 2 29 20-Oct 10-Nov 1 month 96% 54 10 10 0 64 65.1 2 33 17-Oct 8-Dec 2 month 89% 0 92 76 16 92 0.0 2 34 17-Oct 8-Dec 2 month 89% 25 64 60 4 89 28.4 3 26 17-Oct 12-Nov 1 month 89% 11 76 11 65 87 12.5 3 24 17-Oct 12-Nov 1 month 89% 29 54 49 5 83 33.0 3 25 17-Oct 9-Dec 2 month 89% 9 88 62 26 97 10.2 4 21 20-Oct 12-Nov 1 month 96% 79 17 17 0 96 95.2 4 15 20-Oct 8-Dec 2 month 96% 92 7 7 0 99 100.0 4 17 20-Oct 8-Dec 2 month 96% 52 36 34 2 88 62.7 1 18 10-Oct 10-Nov 1 month 0% 0 282 282 0 100 0.0 1 43 10-Oct 10-Nov 1 month 0% 0 102 102 0 102 1 31 10-Oct 9-Dec 2 month 0% 5 56 48 8 61 1 16 10-Oct 9-Dec 2 month 0% 9 47 40 7 56 2 4 10-Oct 10-Nov 1 month 0% 0 95 95 0 95 2 3 10-Oct 10-Nov 1 month 0% 0 90 90 0 90 2 5 10-Oct 8-Dec 2 month 0% 0 83 73 10 83 3 14 10-Oct 12-Nov 1 month 0% 0 100 87 13 100 3 12 10-Oct 9-Dec 2 month 0% 0 77 77 0 77 3 10 10-Oct 9-Dec 2 month 0% 0 98 98 0 98 4 38 10-Oct 12-Nov 1 month 0% 0 82 35 47 82 4 37 10-Oct 12-Nov 1 month 0% 0 103 76 27 103 4 42 10-Oct 8-Dec 2 month 0% 0 71 35 36 71
31 survival S(%)=[n/(i-m)]*100
98
APPENDIX 3-E: Intra-gravel dissolved oxygen measurements
Date Habitat section
Hummock DO (mg/l) Date Habitat
section Hummock DO (mg/l)
Oct. 2002 channel 10.5 Jan. 2003 channel 6.8Oct. 2002 channel 10.3 Jan. 2003 channel 6.0Oct. 2002 channel 10.2 Jan. 2003 channel 11.6Oct. 2002 channel 9.9 Jan. 2003 channel 11.8Oct. 2002 channel 9.4 Jan. 2003 channel 12.3Oct. 2002 channel 10.2 Jan. 2003 channel 4.6Oct. 2002 channel 10.6 Jan. 2003 channel 12.6Oct. 2002 channel 9.7 Jan. 2003 channel 12.0Oct. 2002 channel 10.3 Jan. 2003 channel 11.9Oct. 2002 channel 9.4 Jan. 2003 natural 12.9Oct. 2002 channel 10.0 Jan. 2003 natural 13.2Oct. 2002 channel 10.0 Jan. 2003 natural 13.0Oct. 2002 channel 8.9 Jan. 2003 natural 13.1Oct. 2002 channel 10.5 Jan. 2003 natural 13.1Oct. 2002 channel 10.5 Jan. 2003 natural 13.2Oct. 2002 channel 10.4 Jan. 2003 natural 13.4Oct. 2002 channel 9.5 Jan. 2003 natural 13.3Oct. 2002 channel 10.0 Jan. 2003 natural 13.3Oct. 2002 channel 10.3 Jan. 2003 natural 13.0Oct. 2002 channel 10.3 Jan. 2003 natural 13.1Oct. 2002 channel 9.3 Jan. 2003 natural 13.1Oct. 2002 channel 9.9 Jan. 2003 natural 13.1Oct. 2002 channel 9.8 Jan. 2003 natural 13.2Oct. 2002 channel 11.0 Jan. 2003 natural 13.2Oct. 2002 channel 9.6 Jan. 2003 natural 13.1Oct. 2002 channel 10.4 Jan. 2003 natural 13.2Oct. 2002 channel 10.5 Jan. 2003 natural 13.0Oct. 2002 channel 10.4 Jan. 2003 channel 5.2Oct. 2002 channel 10.0 Jan. 2003 channel 5.9Oct. 2002 natural 12.6 Jan. 2003 channel 6.2Oct. 2002 natural 11.6 Jan. 2003 channel 8.6Oct. 2002 natural 11.5 Feb. 2003 channel 13.2Oct. 2002 natural 11.9 Feb. 2003 channel 11.6Oct. 2002 natural 10.4 Feb. 2003 channel 12.5Oct. 2002 natural 10.4 Feb. 2003 channel 11.8Oct. 2002 natural 10.6 Feb. 2003 channel 10.4Oct. 2002 natural 11.2 Feb. 2003 channel 8.8Oct. 2002 natural 11.2 Feb. 2003 channel 9.8Oct. 2002 natural 10.6 Feb. 2003 channel 8.6Oct. 2002 natural 10.1 Feb. 2003 channel 13.1Oct. 2002 natural 10.5 Feb. 2003 channel 12.8Oct. 2002 natural 11.2 Feb. 2003 natural 12.8Oct. 2002 natural 13.4 Feb. 2003 natural 11.8Oct. 2002 natural 10.3 Feb. 2003 natural 11.8Oct. 2002 natural 10.7 Feb. 2003 natural 12.0Oct. 2002 natural 11.2 Feb. 2003 natural 13.1Oct. 2002 natural 10.5 Feb. 2003 natural 12.4Oct. 2002 natural 9.7 Feb. 2003 natural 13.1Oct. 2002 natural 10.6 Feb. 2003 natural 12.4Oct. 2002 natural 10.7 Feb. 2003 natural 12.4Oct. 2002 natural 10.7 Feb. 2003 natural 10.8Oct. 2002 natural 10.6 May-03 channel 7.9Oct. 2002 natural 10.9 May-03 channel 8.5Oct. 2002 natural 11.0 May-03 channel 9.6Oct. 2002 natural 10.9 May-03 channel 9.0Oct. 2002 natural 10.7 May-03 channel 9.3Oct. 2002 natural 10.0 May-03 channel 9.4Oct. 2002 natural 10.7 May-03 channel 8.8
99
APPENDIX 3-F: Fine sediment accumulation within incubation baskets
Weight of sediment fraction (g)
Study site
Placement date
Recovery date 1mm 0.5mm 0.25
mm 0.150 mm
0.037 mm
<0.037 mm
Total wt. (g)
Coarse D50 (cm)
Vol.Fines (ml)
Vol.Coarse (ml)
Total Volume
(ml) Fines % 32
1 10-Oct 10-Nov 91.52 0.02 95.96 37.25 12.12 0.71 237.58 28 145 1400 1545 9.95% 1 17-Oct 10-Nov 21.27 89.45 97.90 28.14 6.10 0.44 243.86 33.5 115 1300 1415 7.38% 1 10-Oct 10-Nov 39.17 46.04 0.00 24.30 18.51 1.66 139.14 24 115 1300 1415 7.38% 1 10-Oct 9-Dec 1.22 7.26 8.45 4.11 3.90 1.19 26.83 27 15 1400 1415 1.03% 1 17-Oct 9-Dec 9.75 24.69 10.03 4.03 1.13 0.11 49.74 30 25 1300 1325 1.60% 1 10-Oct 9-Dec 1.58 7.25 5.81 4.82 4.34 0.94 24.74 29 15 1400 1415 1.03% 2 10-Oct 10-Nov 42.45 30.08 0.05 15.93 8.80 0.99 99.33 24 60 1200 1260 3.62% 2 10-Oct 10-Nov 10.75 82.69 64.51 23.89 21.16 1.15 204.31 24 110 1400 1510 7.54% 2 20-Oct 10-Nov 1.54 5.82 5.17 5.55 5.74 0.83 24.87 26 20 1300 1320 1.28% 2 10-Oct 8-Dec 92.38 234.01 83.03 4.60 7.08 0.68 421.80 25.5 200 1500 1700 14.73% 2 17-Oct 8-Dec 27.46 74.89 32.76 10.69 6.08 0.90 152.78 30 80 1300 1380 5.13% 3 17-Oct 12-Nov 7.38 17.35 12.74 7.84 5.35 0.83 54.10 35 20 1300 1320 1.28% 3 17-Oct 12-Nov 13.34 0.08 18.84 12.01 4.37 0.55 49.52 32 20 1300 1320 1.28% 3 10-Oct 12-Nov 7.48 0.08 4.07 3.85 5.19 1.60 22.27 28 100 1200 1300 6.03% 3 10-Oct 9-Dec 38.46 0.09 9.03 6.15 8.27 2.14 72.12 25.5 35 1200 1235 2.11% 3 10-Oct 9-Dec 19.83 30.39 15.34 9.34 7.01 1.26 83.78 28 35 1300 1335 2.25% 3 17-Oct 9-Dec 14.03 27.90 11.38 3.02 1.32 0.16 57.88 40 30 1300 1330 1.93% 4 20-Oct 12-Nov 1.91 6.01 4.10 3.75 4.36 1.04 21.39 37 15 1400 1415 1.03% 4 10-Oct 12-Nov 7.66 15.26 8.63 3.91 2.24 0.22 38.71 28 20 1200 1220 1.21% 4 10-Oct 12-Nov 4.31 35.52 30.50 13.33 5.74 0.86 90.26 29 55 1200 1255 3.32% 4 20-Oct 8-Dec 3.57 12.01 9.20 7.80 7.38 1.64 41.60 35 30 1400 1430 2.06% 4 10-Oct 8-Dec 6.27 5.40 3.86 3.39 3.96 1.00 23.95 28 90 1300 1390 5.78% 4 20-Oct 8-Dec 4.30 7.16 6.72 7.00 7.97 2.68 35.83 34 25 1300 1325 1.60%
*
32 %f = volume of fines /(volume of basket -volume of coarse substrate)
100
APPENDIX 3-G: Summary of sockeye built and artificial redd measurements
Year Reach Redd builder
Trough depth
(h1; cm)
Hummock depth
(h2; cm)
h1-h2 (m)
Distance h1 to h2
(m)
Redd steepness
D50 Basket or hummock
Fines (%) Gravel % Egg
Survival (%)
2003 channel artificial 28 18 0.10 0.60 0.17 34 7.4% 45.5% 20.5 2003 channel artificial 33 20 0.13 0.63 0.21 28 9.3% 49.0% 2003 channel artificial 31 14 0.17 0.60 0.28 24 7.4% 45.5% 63.9 2003 channel artificial 29 12 0.17 0.48 0.35 30 1.6% 45.5% 40.9 2003 channel artificial 30 12 0.18 0.52 0.35 29 1.0% 49.0% 2003 channel artificial 32 14 0.18 0.46 0.39 27 1.0% 49.0% 2003 channel artificial 42 28 0.14 0.73 0.19 30 5.1% 45.5% 28.4 2003 channel artificial 36 20 0.16 0.83 0.19 24 3.8% 42.0% 2003 channel artificial 44 28 0.16 30 45.5% 2003 channel artificial 40 24 0.16 0.83 0.19 26 1.3% 45.5% 65.1 2003 channel artificial 39 21 0.18 0.63 0.28 24 7.1% 49.0% 2003 channel artificial 42 18 0.24 0.82 0.29 26 12.8% 52.4% 2003 natural artificial 20 12 0.08 0.73 0.11 35 1.3% 45.5% 33.0 2003 natural artificial 23 14 0.09 0.68 0.13 34 49.4 2003 natural artificial 29 11 0.18 0.52 0.35 28 2.2% 45.5% 2003 natural artificial 26 8 0.18 0.58 0.31 26 2.2% 42.0% 2003 natural artificial 33 8 0.25 0.57 0.44 28 6.4% 42.0% 2003 natural artificial 32 1.3% 45.5% 12.5 2003 natural artificial 12 40 1.9% 45.5% 10.2 2003 natural artificial 35 23 0.12 0.62 0.19 35 1.9% 49.0% 110.8 2003 natural artificial 28 15 0.13 0.67 0.20 37 1.0% 49.0% 95.2 2003 natural artificial 24 10 0.14 0.65 0.22 28 5.8% 45.5% 2003 natural artificial 35 21 0.14 0.73 0.19 34 1.6% 45.5% 62.7 2003 natural artificial 26 9 0.17 0.72 0.24 28 1.3% 42.0% 2003 channel sockeye 44 40 0.04 0.78 0.05 32 2002 channel sockeye 60 52 0.08 0.66 0.12 37 2003 channel sockeye 43 34 0.09 1.35 0.07 29 2002 channel sockeye 67 56 0.11 0.63 0.17 39 2003 channel sockeye 64 53 0.11 0.70 0.16 25 2003 channel sockeye 55 43 0.12 1.08 0.11 21 2002 channel sockeye 58 45 0.13 0.92 0.14 26 2002 channel sockeye 62 48 0.14 1.03 0.14 30 2002 channel sockeye 44 30 0.14 0.62 0.23 42 2002 channel sockeye 60 46 0.14 0.83 0.17 22 2003 channel sockeye 35 19 0.16 0.95 0.17 32 2003 channel sockeye 56 40 0.16 1.15 0.14 2003 channel sockeye 36 18 0.18 1.37 0.13 36 2003 channel sockeye 70 52 0.18 1.17 0.15 34
101
Year Reach Redd builder
Trough depth
(h1; cm)
Hummock depth
(h2; cm)
h1-h2 (m)
Distance h1 to h2
(m)
Redd steepness
D50 basket or hummock
Fines (%) Gravel % Egg
Survival (%)
2003 channel sockeye 52 34 0.18 0.77 0.23 25 2002 channel sockeye 60 40 0.20 1.27 0.16 22 2003 channel sockeye 50 29 0.21 0.67 0.32 24 2002 channel sockeye 80 58 0.22 0.90 0.24 36 2003 channel sockeye 48 22 0.26 1.15 0.23 30 2002 channel sockeye 67 40 0.27 0.85 0.32 29 2002 natural sockeye 61 54 0.07 0.63 0.11 23 2003 natural sockeye 29 22 0.07 1.08 0.07 31 2003 natural sockeye 33 26 0.07 0.93 0.08 25 2002 natural sockeye 28 18 0.10 0.75 0.13 38 2002 natural sockeye 30 20 0.10 0.90 0.11 30 2003 natural sockeye 32 21 0.11 0.78 0.14 38 2003 natural sockeye 45 34 0.11 1.02 0.11 40 2002 natural sockeye 71 59 0.12 0.98 0.12 31 2003 natural sockeye 28 16 0.12 1.07 0.11 24 2003 natural sockeye 26 14 0.12 1.10 0.11 50 2003 natural sockeye 29 17 0.12 1.27 0.09 33 2002 natural sockeye 74 61 0.13 1.03 0.13 24 2002 natural sockeye 60 45 0.15 0.85 0.18 23 2002 natural sockeye 35 19 0.16 0.70 0.23 26 2003 natural sockeye 30 14 0.16 1.22 0.13 30 2002 natural sockeye 80 63 0.17 0.95 0.18 33 2003 natural sockeye 48 27 0.21 1.42 0.15 23 2002 natural sockeye 66 43 0.23 0.83 0.28 28 2003 natural sockeye 55 32 0.23 1.47 0.16 27 2002 natural sockeye 56 27 0.29 1.57 0.19 2002 natural sockeye 34 21 0.13 1.15 0.11 2002 natural sockeye 50 36 0.14 1.25 0.11 2002 natural sockeye 67 51 0.16 0.98 0.16 2002 natural sockeye 57 38 0.19 1.27 0.15
Curriculum Vitae Karilyn Ingrid Long
Universities Attended
University of Victoria, 1998, Bachelor of Science (Geography)
Publications
Long, K. and C. Fisher. Evaluation of a proposed experimental re-introduction of
sockeye salmon into Skaha Lake, British Columbia. In-progress
Conference Presentations
The experimental reintroduction of sockeye into Skaha Lake, British Columbia. At
“Water – Our limiting resource” Towards Sustainable Water Management in the
Okanagan. February 23-25, 2005. B.C. Branch, Canadian Water Resources
Association (CWRA)
